tag. is used to display preformatted text on the Web page. By default, the tag uses monotype, so it can be very effective in displaying uniform Web pages across client platforms and browser orientations.
Designing For Web Access Those who were Oracle developers in the 1980s may remember how the advent of Microsoft Windows introduced new design issues. The process of designing Windowsbased front ends for Oracle database applications is very different than designing for a 24×80 fixed-screen display. The addition of Windows’ Graphical User Interface (GUI) constructs brought a host of new widgets previously unknown to the Oracle developer. These widgets included: • • • • •
Radio buttons—Used to indicate mutually exclusive choices. Checkboxes—Used to indicate multiple choices. Pop-up lists—Used to display valid values for a field. Font size control—Used to create screens with many font styles and sizes. Text areas—Used to present scrollable, freeform text display areas.
Early efforts from mainframe developers at using these widgets to develop online Windows applications were both humorous and disturbing. Checkboxes were used where radio buttons were appropriate, text was shrunk into incomprehensibly tiny font sizes, and the misuse of Windows controls made some applications very difficult to understand. It wasn’t until the general acceptance of the Windows Standard Development Kit (SDK) that generally acceptable usage was adopted for Windows widgets. Today, the development of WebServer pages also presents new features, and the new Web features have just as much potential for misuse as the new Windows widgets in the 1980s. The introduction of the World Wide Web has brought new widgets and screen constructs previously unknown to MS-Windows experts. Knowledge of these features and of their uses is critical to the delivery of WebServer applications. The new Web widgets and features include:
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• Web page scroll bars—Unlike a 24×80 screen, a Web page can be of indefinite length, and Web browser scroll bars are used to page through documents. This feature saves the Oracle developer a cumbersome chore, because SQL cursors do not have to be declared and mapped onto screens a few rows at a time. • Browser display size and font—This feature of Web browsers continues to plague WebServer developers because adjustment to the size of the Web browser window can cause an input field to fall out of alignment. • Frames—Independent display and refresh areas can be mapped onto a single Web page. In addition, frames can be nested within other frames, providing recursive levels of screen display. • Tables—Tables can be used to format Web page content into columns, providing for multicolumn display of text and images. • Hyperlinks—Easy to implement links can be added to transfer to other Web pages anywhere in the world. • Dynamic page generation—Web page content can be customized according to user preferences and interactive responses. • Clickable images and image maps (ISMAP)—Dazzling animated images can be used as menus, providing a level of choice unknown to Windows-based front ends. Web Page Scroll Bars In a Web page there are none of the cumbersome chores involved in mapping out repeating groups of data. Unlike a one-page display screen, such as a SQL*Forms or PowerBuilder screen, a Web page will display all of the repeating values on a single document. Since the entire Web page is in a single document, the Web page will allow the end user to use the scroll keys to traverse through the text of the Web page. From a developer’s perspective, this approach is beneficial, because each “repeating” list of data items does not have an array subscript to manage. For example, a repeating list of customer names will not be subscripted customer_name(1), customer_name(2), and so on. Since HTML documents do not support these arrays, the Oracle developer must come up with a method for uniquely referencing these repeating values within their WebServer application. Browser Display Browser display is a continuing problem for WebServer developers who want to deliver uniform end user screens. Unlike traditional screens, where the font and text styles are directly controlled by the developer, Web browsers allow the end user to adjust the font, font style, and alignment of text within the documents displayed in the browser. Consequently, there is no way to ensure that a Web page will always display well-aligned text, and the Oracle developer must struggle to create Web pages that cannot guarantee display format.
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Web Frames A frame is an internal window within a Web page. Using frames, multiple HTML documents can be simultaneously viewed and manipulated from within a single Web browser window. When using frames, changing a value within one frame may cause different information to display in the other page frames. For example, consider Figure 5.5 where the value of the customer ID field determines the contents of three separate frames on the Web page. Each frame can be scrolled independently of each other, providing complete access to all of the requested information. Each time a new customer ID is chosen, the contents of the other page frames are updated to reflect the choice. Each frame is refreshed independently of other frames on the Web page, so frames can greatly improve the performance of your WebServer application.
Note: For details on using frames with WebServer, see htp.frame in Chapter 7, WebServer’s HTP Utilities.
Figure 5.5 Sample frame layouts for WebServer pages. Another popular use for frames is for Web page Help functions. When help is requested, a frame appears in a portion of the Web page, and the Help frame can be manipulated independently from the other frames on the page. Frames are also popular when designing a custom search engine for your Oracle database. One frame could accept the search command, another frame could display the results of the search, and the remaining frames would not file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch05/127-130.html (1 of 3)4/03/2005 6:15:33
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change.
Note: The concept of frames was new with Netscape version 2.0. Not all Web browsers support frames, therefore a special tag called <![CDATA[ is used on many HTML documents so that non–frame-enabled browsers will still be able to access Web pages containing frames. When defining frames, it is important to note that any URL on the Internet can be added to a frame. Frames can also display output from Java applets. Frames can also be nested, or placed within other frames. Each of these frames, in turn, contains the URL to other Web pages, which can also be composed of frames.<br />
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The tags <FRAMESET> and <FRAME> are used within an HTML document to define frame windows. The <FRAMESET> tag is used to define the number of frames and frame sizes. Following are some examples of <FRAMESET> and <FRAME> tags: <FRAMESET ROWS="100, 100, 100"> <FRAMESET COLS="25, 25, 25"> <FRAME SRC="main_menu.html" NAME="internal_name" SCROLLING=auto> In the examples, the first HTML tag would create three vertical rows that are 100 pixels deep. The second tag would creates three columns that are 25 pixels wide. The last tag specifies the HTML document that will reside in the frame and the scrolling options for the HTML document. The <FRAME> and <FRAMESET> tags are used within HTML documents and htp.frame defines a frame for an Oracle WebServer page. Web Tables Tables are used as a formatting tool for Web pages to control the spatial positioning of information. Netscape was the first browser to offer table capabilities, and tables are easy tools to use to create well-formatted WebServer pages. Today, any browser that supports HTML 3.0 and above will support the definition of tables. A Web page table can be thought of as a visual representation of an Oracle table. The difference being, that while an Oracle table must contain column values, an HTML table may contain text, graphics, or images. Prior to the introduction of tables, formatting Web pages was very labor-intensive. As we know, text and images on a Web page are left-justified by default and (if no alignment attributes are assigned) concatenate into one very long single-column Web page. With the introduction of tables, designers can control text and images across the entire Web page. Tables can be used in a variety of ways to control the layout of information. For example, consider Figure 5.6. This Web page uses tables to control the display of sports scores.<br />
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Figure 5.6 A sample use of HTML tables in a data display Web page. In addition to column formatting, tables are useful within Oracle WebServer to design data input forms. Information gathered from Oracle tables can be formatted with borders and file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch05/127-130.html (2 of 3)4/03/2005 6:15:33<br />
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displayed in a clear format.<br />
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Note: For more information on the use of tables for designing Oracle tables, see htp. Table functions in Chapter 7, WebServer’s HTP Utilities.<br />
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Hyperlinks Just as the old-fashioned Personal Function (PF) keys were used within an SQL*Forms application to transfer control to another screen, hyperlinks are used within a WebServer application to transfer control to another Web page. However, there are several important differences between the traditional method of screen transfer and those afforded by the use of hypertext links in WebServer: • A hyperlink can be used to transfer to any Web page, anywhere on the Internet. As such, links outside your WebServer application are now very easy to create. Unfortunately, transferring back from an external Web page may be impossible unless the end user is directed to use the Web browser buttons to return to your WebServer application. Of course, hyperlinks to pages outside your WebServer screen domain should be carefully controlled. • While hyperlinks may be made to pass parameters to the target Web page, database currencies are not easily passed between pages. Consequently, maintaining your place in your Oracle database depends upon careful programmatic solutions. See Chapter 11, WebServer Navigation And Concurrency Management, for more information on controlling Oracle currency and database access. • Most Net browsers feature buttons at the top of the window, as well as menu commands, allowing end users to browse backward and forward (see Figure 5.7). These browser buttons allow the end users to bypass any flow control mechanisms that you may have designed into your architecture.<br />
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Figure 5.7 The Netscape Back and Forward buttons and menu commands. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch05/130-134.html (1 of 4)4/03/2005 6:15:34<br />
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Unfortunately, hyperlinks are one of the easiest Web mechanisms to implement. This is unfortunate because of the widespread misuse of hyperlinking in many Web-based applications. Complex application systems generally must have a well-defined flow of control between screens, but hyperlinks are commonly overused to the point where it is very easy for your end user to become “lost in cyberspace” (see Figure 5.8).<br />
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Figure 5.8 Hyperlinking can take the user to unexpected places. Unlike traditional Personal Function keys for transferring application control, a WebServer application may use several different methods for allowing the end user to transfer to another WebServer page. Table 5.2 summarizes the possible ways that hyperlinks can be implemented. Table 5.2Possible Web hyperlink techniques. GUI Widget<br />
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HTML<br />
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Oracle WebServer<br />
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Standard hyperlinks<br />
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<A HREF rel="nofollow"><br />
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Push buttons<br />
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<SUBMIT><br />
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htp.formSubmit<br />
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Clickable images<br />
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<IMG><br />
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htp.formImage<br />
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There are a variety of methods used for transferring control to another Web page, so it needs to be clear to the end user that the widget does indeed transfer control. This is not always selfevident because push buttons and hyperlinks can be given misleading names.<br />
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Note: For detailed information on controlling the internal WebServer application navigation, see Chapter 10, Managing WebServer Forms And Security.<br />
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Dynamic Page Generation Unlike traditional applications, end-user preferences and selections from Web pages can be used to create customized screens. Remember, the main purpose of Oracle WebServer is to create dynamic Web pages where Oracle table data is embedded into an HTML document, viewed by end users. One of the natural consequences of this powerful feature is that Oracle WebServer applications may customize entire pages according to the preferences of individual end users. In fact, end users could customize their pages to the point that it may not become apparent that two end users are accessing the same application! In any case, the power of WebServer to create user-customizable pages is very impressive, but again, there is potential for abuse. It could be argued that all Web pages are dynamically generated from Oracle because Oracle data is embedded into the HTML at runtime. However, dynamic page generation in this context refers to the ability of the WebServer application to customize most of the Web page attributes, including:<br />
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• Frame contents • Background wallpaper and colors • Table formatting Care should be taken when using dynamic page generation because the application logic can become very cumbersome. To illustrate, consider the following example. For our example, assume that a Web-based Oracle application is designed to serve as a vehicle for placing orders for a mail-order warehouse. Developers want to target advertisements and specials according to customer demographics. Consequently, there are two profiles for end-user customers. One profile is comprised of customers whose previous purchases are for items with an average cost of less than $100 (ordinary customers), while the other profile is comprised of customers whose previous purchases are for items with cost averages more than $100 (big_spender customers). As users identify themselves to the WebServer application, internal logic classifies each customer, and the display is configured according to the customer’s profile. For marketing purposes, a billboard image may be defined within the Web page to display a customized advertising image, just as a billboard might advertise products in a storefront. In addition, big_spender customers might receive an image message offering a discount on expensive jewelry, while ordinary customers will receive an image offering discounts on less expensive household items. Listing 5.1 shows how a PL/SQL stored procedure could be used to classify a customer. Listing 5.1 A sample function to classify a customer type. create or replace function get_customer_type (cust_id varchar2) return boolean is average_price real; declare c1 is select avg(item_price) from line_item, item, order where order.customer_id = :cust_id and order.customer_id = line_item.customer_id and line_item.item_nbr = item.item_nbr; BEGIN open c1; fetch c1 into average_price; if average_price > 100 then { return true else return false end if; end get_customer_type;<br />
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Now that the boolean value of big_spender and ordinary customers has been set, the WebServer application can test this value to determine the appropriate images and frames to place on the dynamic Web page. This type of application has the benefit of being encapsulated in the sense that a single Web page (corresponding to a single Oracle stored procedure) controls all the logic involved in the display of the Web page. There will be a single procedure governing the display of the Web page for all customer profiles, although the processing logic in the PL/SQL may become rather complex. The alternative is to design two Web pages, one for each customer profile. This involves redundant coding of the common characteristics of the Web page but has the benefit of isolating each profile into an independent stored procedure. In any case, the ability to dynamically model Web pages is a very powerful feature of Oracle’s WebServer, and it is a feature that requires careful up-front planning. Clickable Images And Image Maps The use of clickable images to transfer control within Web applications has become almost a de facto programming standard on the World Wide Web. Instead of presenting your end user with a main menu that consists of push buttons, it has become customary to hire a graphic artist to create beautiful images that serve as menus for Web-based systems. It should become apparent that the use of clickable images is a powerful tool for drilldown menus in a WebServer application, but this power does not come without a cost.<br />
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Using Oracle WebServer, it is very easy to invoke the htp.Image procedure to create a clickable image. The htp.Image procedure will track the coordinates of the end user’s mouse as they scan the image, and it will pass the row and column pixel coordinates to a transfer routine when the image is clicked. This is the easy part! The programming challenge comes into play when the receiving Web page accepts the row and column pixel coordinates and uses them to decide which Web page should be invoked. Note in Figure 5.9 that the pixel coordinates are displayed at the bottom of the browser screen, after the question mark. These row and column pixel coordinates will be sent to the receiving routine (in this example, omihome.map) to determine which page will be accessed next.<br />
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Figure 5.9 The Web page for Oracle Magazine with a clickable image map. Images, when used properly, can create a very pleasant front end for an Oracle database application. Vendors are rushing to meet the demand for images by producing CD-ROMs packed with GIF and JPEG images. It is also very easy to capture an image from any Web page. For example, using Netscape, simply place your mouse over the image and hold down the right-hand mouse button (see Figure 5.10). A menu will appear allowing the local capture of the GIF or JPEG image.<br />
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Figure 5.10 Using Netscape to capture an image.<br />
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Note: While it is very easy to capture an image that you find on the Internet, you should be aware that many images are protected by copyright. Consequently, it is important to get the written permission of the owner of the image before using the image on a Web page.<br />
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WebServer Analysis And Design By now, it should be apparent that designing an Oracle application for use with a Web page front end is very different from traditional application design. This section will explore the major design issues involved when creating Oracle WebServer applications and will describe how the knowledgeable Oracle developer can create effective and credible Oracle systems while exploiting the power of Web-based file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch05/134-138.html (2 of 3)4/03/2005 6:15:35<br />
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documents. Designing The Application Framework There are many opinions about the most effective methods for designing application front ends, and there are also many opinions about the proper procedures for creating Web pages. Old-timers may remember when application design involved using a cumbersome IBM product called Basic Mapping System (BMS). With BMS, all rows and columns had to be carefully mapped onto a fixed 24-row by 80-column screen, and it was not uncommon for an experienced developer to spend an entire day formatting an online display screen. This is a far cry from today’s technology, where many children in elementary school are able to create ad hoc Web pages with very little up-front design effort. Common sense dictates that traditional methods of character-based screen designs were a direct result of the time-consuming work involved in defining the screen. Anyone who has ever created a BMS map for an IBM mainframe application will attest that the creation of a screen can take hours of effort and is not easily changed after it has been defined. As a natural consequence, careful planning was required before the actual screen coding began. Today, screen layouts can be easily created and prototyped in minutes, and changes can be tried online almost as fast as the developer can click the mouse. This ease of screen definition has led to a change in attitude about online systems design. Today, the generally accepted method for screen design involves an iterative process whereby the developer successively refines the screen design until the most appropriate screen image has been agreed upon by the end-user community. While this approach is fine for small departmental systems, the development of large Oracle systems requires more forethought, especially when the front end is designed for a Web page. Also, the scope of Web page access is greater than any online systems designers could comprehend, and it is impossible to solicit complete screen preferences from the entire end-user community.<br />
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Systems Analysis For WebServer Pages Fortunately, an approach for the design of Web front ends is very simple and straightforward. Just as with traditional online systems, online design for WebServer applications should follow a top-down approach, where basic goals are defined and successive refinement exposes the application details. The main difference between traditional systems analysis and Web-page systems analysis lies in the determination of when to stop departitioning the functions. For example, whereas a traditional online screen may be able to have 50 separate online screens, the performance limitations of mapping out Web pages may dictate that only 10 Web pages are used, with frames defined within the 10 Web pages to handle additional functionality. The principles of top-down analysis tell us to begin our data flow diagram (DFD) at a very general level. The entire system is viewed as a single process called the Context Level DFD. The DFD is then decomposed, adding levels of detail to the model. The pivotal question becomes, “Where does one stop decomposing the processes?” Any process that could be identified can probably be subdivided to smaller processes, and it is possible to decompose a DFD to the level where each process represents a single statement. An extreme example of functional decomposition would be showing the statement ADD 1 TO COUNTER as a separate process on the data flow diagram. Just as with traditional systems design, the DFD should be decomposed to the Functional Primitive level, where each process bubble performs one granular function. Under this definition, one could consider that the place_an_order behavior performs only one function and is therefore a functional primitive process. When designing for WebServer, the level of decomposition should correspond to a table operation so that each behavior operates on only one object within the Oracle database. This allows the use of triggers within Oracle and greatly simplifies the systems design. In our example, an insert trigger is placed on the ORDER table. This trigger checks the INVENTORY table for items’ instock levels and also checks the CUSTOMER table for the customer credit rating.<br />
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Figure 5.11 shows a level 1 Data Flow Diagram (DFD) for a customer process. In this diagram, we see that the basic function of the Web page is for an online customer to place an order. As part of this process, three Oracle tables are accessed. We must check the INVENTORY table to ensure that adequate stock is on hand, we must access the CUSTOMER table to ensure that the customer possesses a proper credit rating, and we must update the ORDER table to reflect the placing of the order.<br />
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Figure 5.11 A context-level data flow diagram for a WebServer process. While our Web page may have only a single page for the place_order process, it is clear that there will be a good amount of Oracle activity within this page. For object-oriented relational databases, it is better to continue to decompose the place_order behavior into its subprocesses, namely check_credit, add_order, check_inventory_level, decrement_inventory, and add_line_item. These are all subprocesses within the place_order behavior, as shown in Listing 5.2. Listing 5.2 A high level process breakdown. place_order ( check_credit(SELECT on CUSTOMER) add_order(INSERT on ORDER) check_inventory_level(SELECT on ITEM) decrement_inventory(UPDATE on ITEM) add_line_item(INSERT on LINE_ITEM) ) To see the complete details for this Web page, further refinement of the DFD is required as shown in Figure 5.12. Here we see that the place_order process has been departitioned into three subprocesses, and the data flow between each is described.<br />
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Figure 5.12 A level-zero data flow diagram for a WebServer process. If we assume that this is the lowest-level DFD, then how will these processes map to our Web pages? This is the crux of the issue, and one that requires an intimate knowledge of each process. After all, the real point of systems analysis is to make the developer intimate with the logical processes so that they can better understand how these logical processes are mapped into physical Web pages. Now that we have completed the systems analysis for the Web page, we are free to look into the screen design issues as they apply to our WebServer application. Of course, systems design is very different from systems analysis. Whereas systems analysis determines the processes and interaction with the Oracle tables, the systems design process is intended to determine which processes will have Web pages and how the Web pages will<br />
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interact with one another. Special attention needs to be given to the needs of the Web front end, and we need to ensure that our WebServer application is simply defined, following intuitive navigation rules. Once the overall framework for the WebServer application has been designed, the next step is to create task flow diagrams. A task flow diagram is a technique where the processes required to complete a specific task are listed and the screen layouts are associated with the tasks. Consider Listing 5.3 for our customer-order system. Listing 5.3 A detailed level process breakdown. Place an order: Enter customer information accept customer name accept customer shipping address accept customer telephone number accept customer shipping mode accept customer payment method Enter order information for each item accept product ID validate product ID accept quantity desired check inventory levels if not sufficient_stock_on_hand invoke backorder page end Complete order form Compute order total Verify customer credit If bad_credit invoke COD page Submit order adjust inventory levels create packing list display customer shipping information It should be clear that the process of placing an order is quite involved, and this process will have a great deal of activity against our Oracle database. Now that we have listed the major tasks and their goals, we need to associate these tasks with the appropriate Web pages. This begins the systems design process.<br />
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Systems Design For Oracle WebServer There are two major design issues that need to be addressed at this stage. The foremost consideration is the determination of the hierarchy of Web pages for the application. In WebServer applications, as with all online applications, the systems designer must be cognizant of the number of pages the system will contain. An application can be built very flat as seen in Figure 5.13, where the home page transfers to only one level of subpages.<br />
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Figure 5.13 A flat screen hierarchy representation. On the other hand, Figure 5.14 shows how a WebServer application can be designed with many levels of pages. Some online systems designers might argue that this is a better design approach because each individual Web page performs a finite function. While these levels of pages more clearly describe the individual operations within the online system, there may be problems with this vertical approach to the creation of Web pages.<br />
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Figure 5.14 A sample storyboard for a WebServer application. Because the application will be residing on the Web, you need to take into account several factors. First, you should determine whether it is necessary for each process to reside on its own Web page or whether HTML frames could be used to create subpages within a flatter page structure. Remember, the more complex the navigation pathway in your Oracle WebServer application, the more opportunities for procedural error. Also, a vertical Web page design makes it more difficult for the end user to keep track of her position within the Web page hierarchy. One of the primary goals of preliminary Web page design is to create a clear framework for end users so they know where they can go within a cyberspace domain. To illustrate this concept, consider the hierarchy of Web pages for our fictional mailorder company. The home page consists primarily of a logon screen and a menu that directs end users to a table of contents for the various product categories. The next major function of this system allows the end user to peruse the products, as well as invoke a procedure to order products at any time. Logon screens are especially important when granting access to Oracle databases. To ensure WebServer security, we must gather the end user’s Oracle ID and password, and ensure that we always keep track of our end user as they transfer between Web pages. Remember, we do not have the luxury of opening a single connection with Oracle and holding that connection for the entire duration of their session. Instead, we must develop a method for using pseudoconversational processing with Oracle role-based security to ensure that we always maintain accurate connections with Oracle on an as-needed basis. In addition, we document common Web pages that may be invoked at any time from any Web page. Just as the F1 key in Windows can always be used to invoke a Help page, we need to create a framework where our end user can get access to our common functions. These common functions include: • • • •<br />
<br />
Context-sensitive Help facilities Personal page with ordering preferences Search pages Account summary pages<br />
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Notice that “anywhere” access to these Web pages poses an interesting design problem. If an end user invokes the Help facility (probably with a hyperlink), we need to be able to pass to the facility the context of their help request. This will certainly include the name of the page they were on when they invoked the help facility, and may also contain information about the status of the task they were currently in the process of completing. Once having viewed Help, we must ensure that our end user returns to the proper place in their application without having lost any salient information. While this may seem self-evident, it is not an easy task to freeze an Oracle transaction, transfer to another Web page, and then return to the proper position. While this issue is discussed in depth in Chapter 10, Managing WebServer Forms And Security, suffice it to say that this type of functionality requires detailed forethought from the designer. End users love predictability, and many developers make the design mistake of<br />
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creating systems that are too flexible and nonrigid for their end users. This trap is especially true when designing Web page front ends for applications. One of the cardinal rules for application developers has been “force the end user to follow your rules.” As designers, we must have a mechanism to enforce which screens end users see, which buttons they can use, and the format of all incoming data. It is also tempting for many designers to fail to involve the end users in this stage of design. Remember “the primacy of the user” principle. No matter how elegant and welldesigned your system may be, the alienation of end users from the development of the front end will often lead to disgruntled end users—even if the design is perfect for their needs. End users like to feel involved in the design process whenever possible, even if the developer does not address all of their requests. Now that you have an overall feel for how WebServer analysis and design is different from traditional analysis and design, let’s take a look at the logging features of Oracle’s WebServer.<br />
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Using Audit Logs With Oracle WebServer One of the nicest features of using WebServer is the useful logs that are created. Any time a URL request is received by the Web Listener, entries are made into the logs, and these logs contain some very useful auditing and usage information. WebServer logs are located on the WebServer host in the $ORACLE_HOME/ows2/ log directory. The following logs are found in this directory: • owa_default_service.err—An error log that is very useful for debugging WebServer applications. This log contains: • Date-time stamp • ORACLE WEBSERVER error number and message • ORACLE error number and message • PL/SQL error number and message • OWA service name • Procedure name where the error was encountered • svadmin.log—This is the server administration log for recording all WebServer requests. This log contains: • WebServer server_name • Date-time stamp • Type of GET request • syserr.log—Records system errors • sv8880n.log—Records all incoming requests for the port number (in this example, 8880 is the port number). This log contains: • IP address of the requesting client • Date-time stamp • Type of GET request Because the WebServer logs are kept in ordinary flat files, it is very easy to write programs to show Web page usage by categories of users, as well as tracking individual users. Listing 5.4 shows a sample from the owa_default_service.err log. Here we see that the call to the procedure called s10 contained the wrong number of arguments. Note that this problem can be avoided by defining all stored procedure input values with a default value of NULL. Listing 5.4 A sample from the WebServer owa_default_service.err log. Sun Nov 17 OWS-05101: ORA-06550: PLS-00306:<br />
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14:10:32 1996 Agent: execution failed due to Oracle error 6550 line 1, column 77: wrong number or types of arguments in call to 'S10'<br />
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ORA-06550: line 1, column 77: PL/SQL: Statement ignored OWA SERVICE: OWA_DEFAULT_SERVICE PROCEDURE: s10 The owa_default_service.err log is especially useful for debugging WebServer code. For example, if the URL for a WebServer stored procedure specifies three parameters, while the stored procedure is created to accept four parameters, an error message will be written to this log. You can easily track error messages in the WebServer log by adding the following alias command to your Unix logon script: alias<br />
<br />
log<br />
<br />
'tail -50 $ORACLE_HOME/ows2/log/owa_default_service.err'<br />
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When testing WebServer applications, it is good practice to have a Unix window open, so that when you encounter a WebServer error, you can use the log alias to quickly diagnose the cause of the problem.<br />
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Note: The WebServer log suffers from the same limitations as the Oracle alert log. The WebServer logs are stored as Unix flat files, which will continue to grow indefinitely until they are purged or archived by the WebMaster. In general, it is usually a good idea to “roll-over” the WebServer logs on a periodic basis. For example, the Unix remove command (rm) could be put into a cron task to discard the log contents, followed by the Unix touch command to re-create the log. Another possibility is to archive the WebServer logs to tape using the TAR or CPIO utilities.<br />
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For example, a Unix shell script could be written to count the number of times a particular Web page is requested. In most cases, each Oracle Web page is stored as a separate stored procedure. Listing 5.5 shows a very simple c shell script that will scan the directory where the Oracle stored procedures are kept (assuming that the Unix filenames are the same as the stored procedure names) and produces a count for the number of times that the stored procedure was called by WebServer.<br />
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Note: In Oracle, it is a good practice to give descriptive names to the Unix files that contain the source code for your Oracle stored procedures. For example, the stored procedure with the Oracle name add_customer may be stored in a Unix file called add_customer.sql. If you do not keep your stored procedures in a flat file with the same name as the stored procedures, we could easily enhance the script to read the stored procedure names from the Oracle data dictionary with the SQL command select distinct name from dba_source where type = ‘PROCEDURE’.<br />
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Listing 5.5 A c shell program to count the number of requests for a WebServer page. #! /bin/csh foreach inst ('ls $DBA/source/procedures |cut -d"." -f1') echo The Web page named $inst was requested 'grep $inst sv8880n.log|wc -l' times end In Listing 5.5, the Unix script simply loops through each procedure name and extracts a count for the number of times each procedure was called by the Oracle WebServer. Listing 5.6 is the output from running the script in Listing 5.5. This provides a very useful measure of the number of times that each Web page was called. Listing 5.6 The output from the c shell program to count the number of requests for a WebServer page. The The The The The The The<br />
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Web Web Web Web Web Web Web<br />
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page page page page page page page<br />
<br />
named named named named named named named<br />
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do_host was requested 36490 times e was requested 5813 times error_web_page was requested 337 times formfield was requested 36630 times formtext was requested 8332 times ins_dba was requested 975 times ins_dba_host was requested 450 times<br />
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The The The The The The The The The<br />
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Web Web Web Web Web Web Web Web Web<br />
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page page page page page page page page page<br />
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named named named named named named named named named<br />
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ins_host was requested 330 times s00 was requested 8665 times s10 was requested 1367 times s10a was requested 9347 times s10b was requested 455 times s10uh was requested 87650 times secrets_tables was requested 4340 times update_form was requested 1563 times update_host was requested 57430 times<br />
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WebServer 3.0 Log Features With Oracle WebServer 3.0, a new log server is available. The WebServer 3.0 log server includes the following features: • • • •<br />
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System message formats and client-defined statistics “Spyglass” listener for logging integration with other applications Log archiving utility Log statistics placed in Oracle tables (rather than Unix files)<br />
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In addition, WebServer 3.0 offers a log analyzer tool. This tool will read the WebServer logs and produce graphical reports. The log analyzer allows the generation of reports based on URL addresses, number of times Web pages are accessed, client IP addresses, and other log statistics.<br />
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Summary Now that we have reviewed the basics of WebServer design, we are ready to explore the details of Oracle’s WebServer. The upcoming chapters will cover Oracle’s common gateway interface, the HTP and OWA functions, and detailed information and examples from working WebServer applications. We will then take a look at Web forms management within a WebServer application, navigation between Web pages, and performance and tuning considerations for Oracle WebServer.<br />
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CHAPTER 6 Oracle’s Common Gateway Interface Communication between Web servers and the databases that provide Web browsers with dynamic information is facilitated by an executable program called a gateway interface. The Common Gateway Interface (CGI) is one of the oldest and most widely used gateway interfaces, but Oracle has developed a better implementation of the process called the Web Request Broker (WRB). This chapter discusses CGI as a basis for the WRB technology, because the WRB function processes parameters using the same environment variables as CGI.<br />
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Origins Of CGI Web servers have always been able to present static documents without the assistance of other programs. However, dynamic content, user input, and database interface cannot be accomplished by static documents; dynamic documents need to be used. In actuality, dynamic documents have been around a long time, and have been written in several programming languages. This was made possible by the simplicity of the original HTTP specifications handling the requests. Over time, Web servers have become more complicated and it became apparent that it was not practical to replicate certain functions for every application requiring dynamic documents (such as logging, communications, security, and load management). So Web server developers began to provide interfaces that could execute external file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch06/151-154.html (1 of 3)4/03/2005 6:15:38<br />
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programs, usually in response to a request for a document. The first external-program interfaces were a significant advance, but did not solve the standardization problem. The various Web servers followed separate standards for the development of external programs, so there was no single external program that was useable by all servers. The CGI standard was designed to provide a method for interfacing a database with Web pages. Originally initiated by Rob McCool of the National Center for Supercomputing Applications (NCSA), the early development of CGI was done in the Perl language by Tony Sanders of Berkeley Software Design Incorporated. Credit also needs to be given to Charles Henrich of Michigan State University. Henrich developed a way for Unix servers to incorporate parsed HTML features, which built the foundation for creating dynamic HTML documents.<br />
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Components Of CGI Many of us are familiar with the HTML documents that lie behind the pages we have retrieved on the Web. These can be viewed by choosing View|Document Source in Netscape, or a similar command in most other Web browsers. The HTML documents and the information they contain are static in that they do not change. Static documents are good when you want to precisely control what users can and cannot do with a Web page. On the other hand, if you want Web pages with clickable image maps and fill-in forms that interface with information servers such as Oracle WebServer, NCSA’s HTTPd, and Netscape’s Communications Server, then you’ll want to use an interface such as CGI. CGI programs are executed in realtime as a means to output dynamic documents that are flexible in meeting the changing needs of users. To access a database from the World Wide Web using CGI, the page’s URL needs to be specified as input for the CGI program. When a viewer sends the URL to the server, the CGI program executes and identifies the user’s request. The request is then sent to the database engine for processing, and the results are sent back to the server and then relayed to the viewer’s browser. A common use of CGI programming is to have a Web client use a CGI search program to submit search criteria, perform the search, and return an index or document to the requesting client. Allowing anyone to run a CGI program on your system presents a security risk that needs to be addressed. Unlike standard URLs, CGI programs must reside in a standard directory so that the Web server will know to execute a program rather than display a static page (such as an HTML document) on the requester’s browser. Programming Languages CGI programs can be written in numerous languages, including: • • • • • •<br />
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C or C++ Perl OraPerl FORTRAN TCL All Unix shells (C shell, Bourne shell, Korn shell)<br />
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• AppleScript • Visual Basic<br />
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Note: OraPerl is a version of Perl that has been extended through the Iusersubs feature to allow access to Oracle databases. Using the usub mechanism (see the usub/ subdirectory in the distribution tree) allows the linking of a database library allowing embedded calls to Oracle.<br />
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Programs And Scripts Deciding on the coding language to use for a CGI program is an individual choice. You should base your choice on the software already installed on your system, the experience of the programming staff, and the functionality that you wish to utilize. The listed CGI gateway programs vary dramatically in availability and developer friendliness, depending on the operating system of your server. For instance, Unix allows easy shell and Perl scripting as well as C coding, whereas Macintosh does not permit shell scripts to be used, so AppleScript is your only choice. If your CGI programs are written in a programming language such as C++ or FORTRAN, then in addition to the executable directory (CGI bin), there will also be a source code directory. This means that your CGI programs need to be compiled before execution. CGI programs can also be interpretive (noncompiled) scripting languages such as Perl, OraPerl, TCL, or a Unix shell. In these situations, the CGI programs are called CGI scripts, and only require the CGI executable directory because there is no source code to compile. In general, CGI scripts tend to be easier to code, debug, and modify than compiled CGI programs. Compiled programs, on the other hand, tend to execute faster than interpretive CGI scripts. If your HTTP server is heavily used and the CGI program will be executed frequently, a compiled language would be the faster alternative.<br />
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Environment Variables CGI uses environment variables to send a program or script its parameters. The CGI standard provides the external program with information about the server, the browser, and the user. The main environment variables are query_string and path_info.query_string is represented by whatever follows the first question mark (?) in the URL, and contains the parameters passed to the PL/SQL procedure. This parameter is only used in the GET form method of passing information as input. For example, the following URL executes a program called “entry,” with a query_string of customer=IBM: http://www.oracle.com:8888/ows-bin/owa/entry?customer=IBM This information could be added by an HTML GET form or by an ISINDEX document. This string gets encoded in the standard URL format, replacing special characters with %xx hexadecimal and changing spaces to +. In order to use this URL, it must be decoded. path_info allows for extra information to be embedded within the URL for your gateway to send to the CGI program. This extra information does not get encoded. A very good use for path_info is to send file locations to the CGI program. Adding extra path information to the end of the URL will tell the CGI program the relative location of the file to execute. In the below example, the path_info variable would be the string “/entry,” which is the name of the CGI program (or PL/SQL procedure): http://www.oracle.com:8888/ows-bin/owa/entry?customer=IBM The actual path of the file to be executed is defined by the path_translated environment variable that is generated by the server. The path_translated variable is the full-path directory name pointing to the location of the program on the server. In the following example, the path_translated variable mapped to the service “/ows-bin/owa” would be “/u01/ dba/oracle/app/oracle/product/7.3.2/ows2/bin”: http://www.oracle.com:8888/ows-bin/owa/entry?customer=IBM The service “/ows-bin/owa” is comprised of the Oracle virtual directory mapping “/ows-bin/” and the PL/SQL Agent executable “owa.” Client Documents Once you have retrieved the results from the Web server, you need to send the information back to the client in the form of a document. CGI programs can return documents of various types, including HTML, plain text, image, audio, video, and references to other documents. The Multipurpose Internet Mail Extension (MIME) protocol defines several content types and subtypes that allow programs to recognize different kinds of files and handle them in the appropriate way. The MIME protocol specifies the type of file, such as video or audio, and the subtype indicates the format of the file. The Oracle Web Listener recognizes MIME types by the file name extensions (which are case sensitive) and<br />
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interacts with the CGI program to inform the client of the document type it will receive. Regardless of whether it is a full document or a reference to another document, CGI will request users to place an ASCII-text header on the output. This header is comprised of lines separated by either carriage returns or line feeds (or both) followed by a single blank line. The output body then follows the header and can be a full or reference document. The full document output type is communicated to the server through a MIME type. Some examples of MIME types are text/plain (ASCII only) and text/html (for HTML documents). Listing 6.1 and Figure 6.1 show a sample CGI script outputting an HTML document for a client.<br />
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Figure 6.1 The HTML document from Listing 6.1. Listing 6.1 Sample HTML document. Content-type: text/html <HTML> <HEAD> <TITLE> CGI script outputting HTML </TITLE> </HEAD> <BODY> <H1> Organization Members </H1> Ed Sr, Louise, Ron, Dee, Ed, Bob, Rick, Donna, Craig, Don, Rich, Cheo, Chuck, Forrest, and JC. </BODY> </HTML> The reference document output type tells the browser where to retrieve the document or can output the document automatically (see Listing 6.2 and Figure 6.2). In this example, the document becomes a hypertext link with the anchor tag (<A>) allowing the definition of the hypertext reference (HREF).<br />
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Figure 6.2 The HTML reference document from Listing 6.2.<br />
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Note: You may not even see the HTML text in a reference document, since many of the newer browsers will take you to the new location automatically. When referencing another file that does not enforce access authentication, you only need to specify a partial URL (exclusive of the server name) such as: Location:<br />
<br />
/directoryA/directoryB/test.html<br />
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Referencing a document that enforces authentication requires the full URL to be specified: Location:<br />
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/server/directoryA/directoryB/test.html<br />
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Listing 6.2 Sample HTML source code that references a document. Content-type: text/html Location: http://www.iis-sports.com/sportweb/football/buffalo.html <HTML> <HEAD> <TITLE> It's not here anymore </TITLE> </HEAD> <BODY> <H1> It moved to another location </H1> The new location is <A HREF="http://www.iis-sports.com/sportweb/football/buffalo.html" rel="nofollow"> location </A> </BODY> </HTML><br />
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Image Maps And Forms Most CGI programs are associated with HTML forms and image maps, and serve to process the results of input (the data input to the form or the spot clicked on the image map). Image maps are similar to forms and are activated by clicking on a portion of an image. The specific location of where a user clicks on an image is sent to the server to determine the information that is to be sent back to the user. This procedure is accomplished by using the ISMAP extension embedded in the <IMG> tag and an associated MAP file. All the regions in the image that you can click on are associated with specific URLs through the MAP file. The ISMAP extension makes the image in your document a mapped image, enabling users to click on different parts of the image to retrieve different informational results. Listing 6.3 shows the HTML source code for the image map. Image maps are comprised of three parts: the image, HTML coding to specify the image map areas, called hotspots, and the MAP document. The clickable image map would display a picture of the state of New York as a GIF image and show the cities where we maintain our database servers. Listing 6.3 HTML source code for an image map. <CENTER> <IMG SRC="header-ny.gif"> <BR> <A HREF="http://picsite.com/nys.map" rel="nofollow"><br />
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<IMG ISMAP SRC="nys.gif"> </A> <BR> Choose the city to display database server information </CENTER> Coordinates in our sample image are set for Buffalo, Rochester, and Syracuse. Clicking within the assigned coordinates will call a URL that will transfer the user to a page displaying information about the database server residing in the selected city. You can specify the shape of the hotspot to be a circle, square, rectangle, point, or polygon. These coordinates are stored in the MAP file on the host server and will define the active points on the image. MAP files are formatted differently depending on the Web server being used on the host server. Listing 6.4 displays a sample MAP file, including the coordinates for each of the hotspots shown on the map. As you can see from the code, clicking within the defined 30-pixel radius for a specific city will transfer you to that URL. Clicking in the image map outside of those defined rectangles will default to the URL general.html. If you are not interested in creating the ISMAP data files manually, there are tools available to automate the process for you. Listing 6.4 Image map coordinates. default http://picsite.com/general.html rect (35,40) 30 buffalo.html rect (56,142) 30 rochester.html rect (70,167) 30 syracuse.html Another extension to HTML are forms. Forms allow users to submit input to the host server. There are a few basic HTML forms, including GET and POST. In combination with HTML forms, CGI scripts execute on the Web server, where they receive and process the input sent by users. The HTML opening and closing tags that define a form are <FORM ACTION=URL METHOD=METHOD> and </FORM>. The URL specifies the location of the application script or program that will process the form input, while METHOD displays as either GET or POST. The GET form can only process small amounts of input attached to a URL. This input, which follows a question mark, is appended to the URL, which is then given to the CGI program or script and returned to the Web server. Using a POST form allows the processing of greater amounts of information because the form sends data as a data stream using standard input (stdin), not as a long URL. Your Web page forms can contain any standard HTML tags, as well as some other tags developed specifically for forms. Some of the form tags for input include: • <INPUT>—The types of input include TEXT, PASSWORD (not displayed), CHECKBOX, RADIO (only one button checked), SUBMIT (sends the contents of the form), and RESET (refresh the input fields in the form). • <SELECT>—Grouping of checkboxes. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch06/157-159.html (2 of 3)4/03/2005 6:15:39<br />
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• <TEXTAREA>—Multiple lines of text.<br />
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CGI And Oracle’s Web Request Broker Now that you’ve been presented an overview of the basics of CGI, let’s turn to the Oracle WebServer 2 architecture and see how CGI fits into WebServer. Oracle WebServer has the capability of processing dynamic HTTP requests through the CGI. However, Oracle has also developed their own gateway interface called the Web Request Broker (discussed in Chapter 2), so both options are available. Further details on the differences between these two gateway interfaces are described later in this chapter. An important part of Oracle WebServer is the PL/SQL Agent. The Oracle PL/SQL Agent (formerly known as Oracle Web Agent) provides a standard way for Web clients to invoke Oracle7 stored procedures and create dynamic HTML documents in realtime. The PL/SQL Agent is a procedural gateway that provides an object-oriented and extensible mechanism for producing HTML pages using PL/SQL. PL/SQL is Oracle’s procedural-language extension to SQL and is portable to all operating systems compatible with the Oracle DBMS. Another part of the Oracle WebServer puzzle is the Web Request Broker, which is an asynchronous request handler with an application program interface (API). The API allows the WRB to interface to back-end software called WRB cartridges. The PL/ SQL Agent is one of these cartridges.<br />
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Note: Chapter 4, Installing And Configuring Oracle WebServer, details configuring the virtual directory mappings for access via the WRB and CGI.<br />
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Another component of the WebServer is the Oracle Web Listener (OWL). The OWL passes incoming URLs to CGI programs or WRB cartridges. When OWL is working with CGI, it sends the CGI program requests via standard input, and CGI returns output back to the OWL via standard output. The OWL then sends the output to the browser on the client. Each time the OWL receives a URL request to run a CGI program, it starts a separate process to perform the request. The OWL’s process with WRB is different from its process with CGI, in that WRB eliminates the need to create a new process for every request. When the OWL interfaces with WRB, it is free to receive and evaluate incoming URLs while each request is given to the WRB to execute the desired process in the background. For example, with the WRB, the PL/SQL Agent would stay connected to the Oracle7 DBMS for all requests, thus avoiding a new connection to the database every time a stored procedure is executed. This continual state of connection is called persistence. Persistent connections are what makes WRB a faster process than CGI. Because CGI lacks persistence, server resources are wasted as users are continually re-identified. Persistence is also very important for databases to ensure that transactions are either fully committed or rolled back if necessary. If the connection from browser to database does not stay open and a transaction must roll back, a new transaction must be triggered to complete the operation.<br />
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Note: For more information on the components of Oracle WebServer, see Chapter 2, Oracle WebServer Architecture.<br />
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As mentioned earlier, Oracle WebServer 2 includes both of the methods for implementing the PL/SQL Agent—WRB and CGI. The intent of keeping CGI as an option within Oracle WebServer 2 was for backward compatibility of existing applications, and also because CGI enables the PL/SQL Agent to function with any Web server. If it is feasible in your situation, you should use the WRB interface developed by Oracle for performance reasons and bypass CGI. Additional details on the specific operation of the WRB are found in Chapter 2, Oracle WebServer Architecture.<br />
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Note: If the URL for a request contains the string “owa” in a standard position, the Oracle Web Listener executes the request using the PL/SQL Agent. Whether this is done through the WRB or through CGI depends on how the directory mappings are configured through the Oracle WebServer Administrator and which virtual directories are specified in the URLs. The OWL can communicate with either the WRB or CGI through standard CGI environment variables.<br />
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The Webmaster The Webmaster is the title applied to the person who is responsible for maintaining your Web server. The Webmaster is usually responsible for the CGI directory and should implement restrictions on users. These restrictions involve the creation and execution of CGI programs that assign user privileges. These programs are executed<br />
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by a Unix userid on the HTTP server and should, therefore, offer a range of limited Unix account privileges. For example, in the Oracle WebServer configuration, a lowprivileged Unix user account is called nobody. The nobody Unix user has the necessary privileges to execute CGI programs, but cannot perform DBA-level functions against the database.<br />
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Summary Access across the World Wide Web has been greatly enhanced by the development of interfaces such as the WRB to facilitate dynamic interaction between users and the data resources on the Internet. Exciting times are here for corporations to have their customers retrieve and update data on internal database servers, greatly streamlining repetitive functions such as placing product orders and tracking the status of those orders. Technology is changing rapidly, which is evidenced by the development of newer technologies such as the WRB; an improvement upon the CGI handling of dynamic requests on the Web. Even though CGI is being superseded within the Oracle WebServer architecture by the WRB, it’s still a very popular interface because of its simplicity. Several tools were developed to enhance CGI programming, including some Perl libraries and the cgic library for the C language. These changes will provide better and faster ways of processing information, making our lives easier and helping companies who take advantage of the latest advances remain competitive.<br />
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CHAPTER 7 WebServer’s HTP Utilities In order to provide an interface between native HTML and Oracle’s WebServer, Oracle has developed a method for insulating the native HTML calls. Using WebServer’s methodology, all HTML tags are generated on your behalf. When using the Oracle WebServer, there is a standard library of HTML function calls that are used to create the screen images. While similar in function to standard HTML tags, htp (hypertext procedure) functions are called procedurally from within an Oracle stored procedure. There is a one-to-one correspondence between the htp and htf (hypertext function) libraries, but the htp calls are always used, except when functions need to be embedded, or nested, within a single statement. It is not sufficient to call an htf function because the HTML tag will not be passed to the Oracle PL/SQL Agent. Therefore, it is always necessary to use the htp calls. To understand the difference between an htf and an htp call, let’s consider an example of an embedded htf call. Every htp procedure has a corresponding htf function call, and the htp call should always be used unless there are htf calls that are nested within a single htp call. For example: htp.print(htf.bold('This is a bold title')); In this example, the call<br />
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htf.bold('This is a bold title') will generate: <B>This is a bold title</B> Nesting this htf call within the htp call results in: <H1><B>This is a bold title</B></H1> As a general rule, you may nest as many htf calls as you like, as long as the outermost call is an htp call. Keep in mind that the htp calls will always generate HTML tags on your behalf. For example, the following call htp.headOpen; htp.title('This is the header'); htp.headClose; would be interpreted as: <HEAD> <TITLE>This is the header</TITLE> </HEAD><br />
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HTP/HTF Functional Groupings The hypertext procedures and functions illustrated in this chapter can be grouped into subcategories, based on their common functions. These groupings are outlined here as a functional reference list. Later in the chapter, example code for many of these procedures and functions will be presented in alphabetical order. Print Procedures Print procedures generate HTML tags related to printing information on a Web page. This information can be static or dynamic in content, depending on the request being processed. • • • •<br />
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htp.print htp.prn htp.prints htp.ps<br />
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Structure Procedures Structure procedures generate HTML tags that identify the structures within a Web document. This generally translates to opening and closing sections of HTML code for specific purposes. Each of the following procedures has a corresponding htf function file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/163-169.html (2 of 5)4/03/2005 6:15:41<br />
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to assist in the code-building process. • • • • • •<br />
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htp.htmlOpen htp.htmlClose htp.headOpen htp.headClose htp.bodyOpen htp.bodyClose<br />
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Head Procedures Head procedures generate HTML tags used for processing between the htp.headOpen and htp.headClose procedures. These htp procedures are also available as htf functions, which gives you greater flexibility in your application development. • • • • • • •<br />
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htp.title htp.isindex htp.linkRel htp.linkRev htp.meta htp.bodyOpen htp.bodyClose<br />
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Body Procedures Body procedures generate HTML tags that are processed within the main section of the text. Each of the following procedures has a corresponding htf function to assist in the code-building process. • • • • • • • • • • • • • • • • • • • • •<br />
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htp.line htp.hr htp.nl htp.br htp.header htp.anchor htp.anchor2 htp.mailto htp.img htp.img2 htp.para htp.paragraph htp.address htp.Comment htp.preOpen htp.preClose htp.blockquoteOpen htp.blockquoteClose htp.base htp.area htp.mapOpen<br />
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• • • • • • • • • • • • • • • • • • • •<br />
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htp.mapClose htp.bgsound htp.div htp.listingOpen htp.listingClose htp.nobr htp.wbr htp.center htp.centerOpen htp.centerClose htp.big htp.small htp.sub htp.sup htp.basefont htp.fontOpen htp.fontClose htp.plaintext htp.s htp.strike<br />
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Frame Procedures Frame procedures generate HTML tags that enable a Web page to be subdivided into partitions, or frames. Each of these partitions may be defined with different structures and characteristics to improve the presentation of that section of the document.<br />
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Note: Some Web browsers do not support the use of frames for displaying HTML documents. Review the procedures in detail later in this chapter for alternatives in handling this type of scenario.<br />
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• • • • •<br />
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htp.framesetOpen htp.framesetClose htp.frame htp.noframesOpen htp.noframesClose<br />
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List Procedures List procedures generate HTML tags that provide several options for listing information on a Web page. List procedures have hypertext functions related to each of the following procedures to assist in the code building process. • • • • • •<br />
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htp.listHeader htp.listItem htp.ulistOpen htp.ulistClose htp.olistOpen htp.olistClose<br />
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• • • • • • • •<br />
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htp.dlistOpen htp.dlistClose htp.dlistDef htp.dlistTerm htp.menulistOpen htp.menulistClose htp.dirlistOpen htp.dirlistClose<br />
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Character Format Procedures Character format procedures generate HTML tags used to define the formatting characteristics of text on a Web page. These procedures are also implemented as hypertext functions (htf) to better address the functionality of your document. • • • • • • • • •<br />
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htp.cite htp.code htp.emphasis htp.em htp.keyboard htp.kbd htp.sample htp.strong htp.variable<br />
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Physical Format Procedures Physical Format procedures generate HTML tags that provide formatting options for text such as boldface or italics. Each of these procedures also has a related hypertext function. • htp.bold • htp.italic • htp.teletype Form Procedures Form procedures generate HTML tags that enable the use of forms within a Web page. These forms can accept input in various ways to facilitate dynamic interaction between the user and the Web application. Each htp form procedure has a corresponding hypertext function. • • • • • • • • • • • • •<br />
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htp.formOpen htp.formClose htp.formCheckbox htp.formHidden htp.formImage htp.formPassword htp.formRadio htp.formReset htp.formSubmit htp.formText htp.formSelectOpen htp.formSelectOption htp.formSelectClose<br />
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htp.formTextarea htp.formTextarea2 htp.formTextareaOpen htp.formTextareaOpen2 htp.formTextareaClose htp.formTextareaClose2<br />
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Table Procedures Table procedures generate HTML tags that enable tables to be used within a Web page. They also provide several options, including inserting a row into a table. Each table procedure has a corresponding hypertext function available to further your development capabilities. • • • • • • •<br />
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htp.tableOpen htp.tableClose htp.tableCaption htp.tableRowOpen htp.tableRowClose htp.tableHeader htp.tableData<br />
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HTP/HTF Parameters The hypertext procedures and functions receive varchar2, integer, or date parameters. The first position of the parameter name can be a c for character (varchar2), n for integer, or d for date. The last parameter that may be used by many of the hypertext procedures and functions is cattributes. This optional parameter allows HTML attributes to be sent to the PL/SQL procedure.<br />
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htp.address The htp.address procedure assigns an address to an HTML document. This enables the document to be accessed by its address. Parameters: cvalue(in), cnowrap(in), cclear(in), cattributes(in) • cvalue—Names the address specified for the document (varchar2). Default NULL. • cnowrap—Specifies that wrapping of lines is not allowed (varchar2). Default NULL. • cclear—Determines if you want to insert a new line (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.anchor The htp.anchor hypertext procedure transfers users to another URL. The example used in Listing 7.1 transfers the user to the s10 Web page when an image is clicked. Parameters: curl(in), ctext(in), cname(in), cattributes(in) • curl—URL address of the gateway executable that will access the hypermedia text or image you are linking to (varchar2). • ctext—Hypermedia text or image used as the link (varchar2).<br />
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• cname—Name of the tag that allows it to be a target of a hypermedia link (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL. Listing 7.1 displays a PL/SQL code example using the htp.anchor procedure, and Listing 7.2 shows the HTML code generated by this procedure. Listing 7.1 PL/SQL code using htp.anchor. create or replace procedure anchortst as host_name_in varchar2(20); begin htp.htmlOpen; htp.headOpen; htp.title('anchortst'); htp.header(1,'Oracle WebServer'); htp.header(1,'Anchor Test','C'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's10'); htp.FormHidden('host_name_in', host_name_in); htp.nl; htp.nl; htp.anchor('/ows-bin/owa/s10?host_name_in=host_name_in', htf.img('/ows-img/papaj.gif', 'left','alt_name','', 'HEIGHT=69, WIDTH=100 </IMG> <BR> <H1> Click on Bob for host display/Update </H1>')); htp.print('Host Name: '); htp.FormText('host_name_in',10,50); htp.nl; htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.2 HTML code using htp.anchor. <HTML> <HEAD> <TITLE>anchortst</TITLE> <H1>Oracle WebServer</H1> <H1 ALIGN="C">Anchor Test</H1> </HEAD> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/169-174.html (3 of 4)4/03/2005 6:15:42<br />
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<BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <INPUT TYPE="hidden" NAME="host_name_in" VALUE=""> <BR> <BR> <A HREF="/ows-bin/owa/s10?host_name_in=host_name_in" rel="nofollow"> <IMG SRC="/ows-img/papaj.gif" ALIGN="left" ALT="alt_name" HEIGHT=69, WIDTH=100 </IMG> <BR> <H1> Click on Bob for host display/Update </H1>></A> Host Name: <INPUT TYPE="text" NAME="host_name_in" SIZE="10" MAXLENGTH="50"> <BR> <BR> </FORM> </BODY> </HTML> Figure 7.1 depicts a Web page using htp.anchor.<br />
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Figure 7.1 A sample Web page using htp.anchor.<br />
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htp.anchor2 The htp.anchor2 hypertext procedure defines the beginning and end destinations of a hypertext link. The HREF attribute is defined through the parameter curl and tells us where to target the link. The NAME attribute is defined through the cname parameter and enables the tag to be the target of a hypertext link. The ctarget parameter allows a page to be framed, which is created by setting width and height, and turning on scrolling. Parameters: curl(in), ctext(in), cname(in), ctarget(in), cattributes(in) • curl—URL address of the gateway executable that accesses the hypermedia text or image you are linking to (varchar2). • ctext—Hypermedia text or image used as the link (varchar2). • cname—Name of this tag which allows it to be a target of a hypermedia link (varchar2). Default NULL. • ctarget—Defines this tag with a target name and allows it to be the target of a hypertext link within a frame (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.area The htp.area hypertext procedure defines how you want to shape an image map on the client side of the request process. The region of the image map affected is defined by the input coordinates. Parameters: ccoords(in), cshape(in), chref(in), cnohref(in), cattributes(in) • ccoords—Coordinates for the image map region (varchar2). • cshape—Shape you want defined for the region of the image (varchar2). Default NULL. • chref—Hypermedia link reference (varchar2). Default NULL. • cnohref—Setting for hypermedia link reference (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.base The htp.base hypertext procedure assigns a name to a document’s URL. This name becomes the default window name for all links within the document. Parameters: ctarget(in), cattributes(in) • ctarget—Name assigned to the URL for this document (varchar2). Default NULL. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/174-178.html (1 of 4)4/03/2005 6:15:42<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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• cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.basefont The htp.basefont hypertext procedure enables you to define the font size for the document. This will be the base font size for the entire page. Parameters: nsize(in) • nsize—Defines the base font size for the Web page (integer).<br />
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htp.bgsound The htp.bgsound hypertext procedure enables background sounds to play for the Web page. You simply have to specify the audio file to be sourced. Parameters: csrc(in), cloop(in), cattributes(in) • csrc—Name of the audio file to be played (varchar2). • cloop—Setting to determine if you want the audio clip to be replayed continuously (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.big The htp.big hypertext procedure generates HTML tags that format text using a big font. Displaying text in a larger font can improve the presentation of the Web page. Parameters: ctext(in), cattributes(in) • ctext—Generates the text to be formatted (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.blockquoteClose The htp.blockquoteClose hypertext procedure ends quoted text. Text defined after the tag <BLOCKQUOTE> is closed out by this procedure. There are no input or output parameters related to this procedure.<br />
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htp.blockquoteOpen The htp.blockquoteOpen hypertext procedure begins the section of quoted text defined by the tag <BLOCKQUOTE>. You have the option of wrapping or not wrapping the text. Parameters: cnowrap(in), cclear(in), cattributes(in) • cnowrap—Specifies that there is no wrapping of lines (varchar2). Default file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/174-178.html (2 of 4)4/03/2005 6:15:42<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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NULL. • cclear—Determines if you want to insert a newline (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.bodyClose This htp.bodyClose hypertext procedure indicates where the end of a screen body will be placed. In general, there are no further screen mapping functions following a bodyClose. This procedure has no related parameters.<br />
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htp.bodyOpen The htp.bodyOpen hypertext procedure indicates the end of a header section and the beginning of the screen body. You may add an image into the background of a document to spruce things up a bit. Parameters: cbackground(in), cattributes(in) • cbackground—Adds a background image to a Web page (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.bold The htp.bold hypertext procedure makes printed text appear in a bold font. This is a good feature for emphasizing important information on a page. Parameters: ctext(in), cattributes(in) • ctext—Indicates text to be highlighted (varchar2). • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.strong for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.br The htp.br hypertext procedure is used as an alias for the procedure htp.nl, which submits a new line into the body of an HTML document.<br />
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htp.center The htp.center hypertext procedure centers text on a Web page. This procedure is helpful for arranging the text on the document and improving its readability. Parameters: ctext(in) file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/174-178.html (3 of 4)4/03/2005 6:15:42<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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• ctext—Designates text to be centered (varchar2).<br />
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htp.centerClose The htp.centerClose hypertext procedure ends a section of centered text on a Web page. There are no parameters related to this procedure. The section of centered text is opened by the procedure htp.centerOpen.<br />
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htp.centerOpen The htp.centerOpen hypertext procedure begins a section of centered text on a Web page. There are no parameters necessary for the execution of this procedure. To end the section of centered text, use the hypertext procedure htp.centerClose.<br />
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htp.cite The htp.cite hypertext procedure formats cited text on a Web page. This is a good way to emphasize information displayed on a document. Parameters: ctext(in), cattributes(in) • ctext—Indicates the text to be cited (varchar2). • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.code The htp.code hypertext procedure displays text in code format (usually displayed as monotype). This is useful for outputting text that would be more understandable when displayed as code. Parameters: ctext(in), cattributes(in) • ctext—Indicates the text to be displayed in code format (varchar2). • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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htp.comment This htp.comment hypertext procedure allows you as a developer to place comments within the source code of a Web page. The benefit is that the comments are not visible to the user displaying the document. Parameters: ctext(in) • ctext—Indicates text formatted as a hidden comment (varchar2).<br />
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htp.dirlistClose The htp.dirlistClose hypertext procedure generates an HTML tag that ends a directory list. A directory list is a specially formatted list of items. There are no parameters related to this procedure.<br />
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Note: See procedure htp.dirlistOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.dirlistOpen The htp.dirlistOpen hypertext procedure creates an HTML tag that starts a directory list. The directory list is a specially formatted list of items. Notice that in the Web page shown in Figure 7.2, the items are displayed as bulleted text. This procedure has no parameters for input or output. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/178-183.html (1 of 6)4/03/2005 6:15:43<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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Note: The htp.listItem procedure call must follow the call to procedure htp. dirlistOpen.<br />
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Figure 7.2 A sample Web page using htp.dirlistOpen. Listing 7.3 displays a PL/SQL code example using the htp.dirlistOpen procedure, and Listing 7.4 shows the HTML code generated by this procedure. Listing 7.3 PL/SQL code using htp.dirlistOpen. create or replace procedure dirlist as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.dirlist Example'); htp.headClose; htp.bodyOpen; htp.dirlistOpen; htp.listHeader('Installation Specifications'); htp.listItem('Item 1: Oracle WebServer 2 was installed with Oracle 7.3.2.1'); htp.listItem('Item 2: The operating system is Solaris 2.5 on an Ultra 1'); htp.listItem('Item 3'); htp.listItem('Item 4'); htp.dirlistClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.4 HTML code using htp.dirlistOpen. <HTML> <HEAD> <H1>Oracle WebServer htp.dirlist Example</H1> </HEAD> <BODY> <DIR> <LH>Installation Specifications</LH> <LI>Item 1: Oracle WebServer 2 was installed with Oracle 7.3.2.1 <LI>Item 2: The operating system is Solaris 2.5 on an Ultra 1 <LI>Item 3 <LI>Item 4 </DIR> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/178-183.html (2 of 6)4/03/2005 6:15:43<br />
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</BODY> </HTML><br />
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htp.div The htp.div hypertext procedure partitions a document. Partitioning enables you to place whatever text or images you want anywhere on the Web page. Parameters: calign(in), cattributes(in) • calign—Aligns hypermedia on the document (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL. Listing 7.5 displays a PL/SQL code example using the htp.div procedure, and Listing 7.6 shows the HTML code generated by this procedure. Listing 7.5 PL/SQL code using htp.div. create or replace procedure divprc as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.div Example'); htp.headClose; htp.bodyOpen; htp.div('right'); htp.print('Display Text on Right Partition'); htp.nl; htp.print('This is the Oracle DB Recovery Flamingo'); htp.nl; htp.div('left'); htp.print('Display Image on Left Partition'); htp.nl; htp.img('/ows-img/flamingo.gif'); htp.nl; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.6 HTML code using htp.div. <HTML> <HEAD> <H1>Oracle WebServer htp.div Example</H1> </HEAD> <BODY> <DIV ALIGN="right"> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/178-183.html (3 of 6)4/03/2005 6:15:43<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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Display Text on Right Partition <BR> This is the Oracle DB Recovery Flamingo <BR> <DIV ALIGN="left"> Display Image on Left Partition <BR> <IMG SRC="/ows-img/flamingo.gif"> <BR> </BODY> </HTML> Figure 7.3 depicts the Web page using htp.div.<br />
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Figure 7.3 A sample Web page using htp.div.<br />
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htp.dlistClose The htp.dlistClose hypertext procedure ends a list of definitions. These definitions are listed in an indented format. There are no parameters for this procedure.<br />
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Note: See procedure htp.dlistDef for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.dlistDef The htp.dlistDef procedure creates an HTML tag to build a list of definitions. Terms can be inserted within this list using the htp.dlistTerm procedure. Notice in the Web page displayed in Figure 7.4 that the terms appear in an indented format within the definition list.<br />
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Figure 7.4 A sample Web page using htp.dlistDef.<br />
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Note: To insert the terms within the definition list, the htp.dlistTerm procedure call must follow the htp.dlistDef procedure call.<br />
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Parameters: ctext(in), cclear(in), cattributes(in) • ctext—Identifies the definition list (varchar2). Default NULL. • cclear—Setting for inserting a new line into the document (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL. Listing 7.7 displays a PL/SQL code example using the htp.dlistDef procedure, and Listing 7.8<br />
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shows the HTML code generated by this procedure. Listing 7.7 PL/SQL code using htp.dlistDef. create or replace procedure dlistprc as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.dlistDef Example'); htp.headClose; htp.bodyOpen; htp.dlistOpen; htp.dlistDef('Definition List 1'); htp.dlistTerm('Definition Term 1'); htp.dlistTerm('Definition Term 2'); htp.dlistTerm('Definition Term 3'); htp.dlistTerm('Definition Term 4'); htp.dlistTerm('Definition Term 5'); htp.dlistClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.8 HTML code using htp.dlistDef. <HTML> <HEAD> <H1>Oracle WebServer htp.dlistDef Example</H1> </HEAD> <BODY> <DL> <DD>Definition List 1 <DT>Definition Term 1 <DT>Definition Term 2 <DT>Definition Term 3 <DT>Definition Term 4 <DT>Definition Term 5 </DL> </BODY> </HTML> Figure 7.4 depicts a Web page using htp.dlistDef.<br />
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htp.dlistOpen The htp.dlistOpen hypertext procedure creates an HTML tag to open an indented list of definitions in a definition list. Parameters: cclear(in), cattributes(in) • cclear—Determines if a new line is inserted into the document (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.dlistDef for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.dlistTerm The htp.dlistTerm hypertext procedure generates an HTML tag to list terms within a definition list. The terms are listed in an indented format, following the definition list name. The htp.dlistTerm procedure call must immediately follow the call to the htp. dlistDef procedure. Parameters: ctext(in), cclear(in), cattributes(in) file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/184-186.html (1 of 3)4/03/2005 6:15:43<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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• ctext—Identifies the definition terms (varchar2). Default NULL. • cclear—Determines if a new line is inserted into the document (varchar2). Default NULL. • cattributes—Settings for common HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.dlistDef for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.em The htp.em hypertext procedure is the alias for the procedure htp.emphasis. This alias will highlight the specified text.<br />
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htp.emphasis The htp.emphasis hypertext procedure highlights text specified as input. The type of highlighting employed may vary, but in most instances, the text appears italicized. Parameters: ctext(in), cattributes(in) • ctext—Identifies the text to be emphasized (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.fontClose The htp.fontClose hypertext procedure ends a section of text using special, definedfont settings. There are no parameters necessary for this procedure.<br />
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htp.fontOpen The htp.fontOpen hypertext procedure begins a section of text using special, definedfont settings. This is helpful for making portions of the text stand out. Parameters: ccolos(in), cface(in), csize(in), cattributes(in) • ccolor—Defines a color setting for the text (varchar2). Default NULL. • cface—Defines how the typeface will be characterized (varchar2). Default NULL. • csize—Defines the size characteristic for the text (varchar2). Default NULL. • cattributes—Attribute settings for the HTML tags (varchar2). Default NULL.<br />
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htp.formCheckbox The htp.formCheckbox hypertext procedure inserts checkboxes, which can be clicked on and off.<br />
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Parameters: cname(in), cvalue(in), cchecked(in), cattributes(in) • cname—Defines the internal reference name for the contents of the field (varchar2). The name for each checkbox button should be different because you can make multiple selections. • cvalue—Indicates the value for the checkbox button (varchar2). Default ON. Each checkbox button should have the same value indicating that it was selected. The name of the button should provide distinguishing information for that button. • cchecked—Defines a button as checked (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.9 displays a PL/SQL code example using the htp.formCheckbox procedure, and Listing 7.10 shows the HTML code generated by this procedure.<br />
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Listing 7.9 PL/SQL code using htp.formCheckbox. create or replace procedure formcheckbox (tab_name in varchar2) is cursor cols is select column_name from dba_tab_columns where table_name = upper(tab_name); BEGIN htp.htmlOpen; htp.headOpen; htp.htitle('Query the '||tab_name||' table by checking columns below.'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path||'do_query'); htp.formHidden('tab_name', tab_name); htp.formHidden('COLS', 'dummy'); for crec in cols loop htp.formCheckbox('COLS',crec.column_name); htp.print(crec.column_name); htp.nl; end loop;<br />
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htp.formSubmit(NULL, 'Execute Query'); htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.10 HTML code using htp.formCheckbox. <HTML> <HEAD> <TITLE>Query the dba_tables table by checking columns below.</TITLE> <H1>Query the dba_tables table by checking columns below.</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/do_query" METHOD="POST"> <INPUT TYPE="hidden" NAME="tab_name" VALUE="dba_tables"> <INPUT TYPE="hidden" NAME="COLS" VALUE="dummy"> <INPUT TYPE="checkbox" NAME="COLS" VALUE="OWNER"> OWNER <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="TABLE_NAME"> TABLE_NAME <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="TABLESPACE_NAME"> TABLESPACE_NAME <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="CLUSTER_NAME"> CLUSTER_NAME <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="PCT_FREE"> PCT_FREE <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="PCT_USED"> PCT_USED <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="INI_TRANS"> INI_TRANS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="MAX_TRANS"> MAX_TRANS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="INITIAL_EXTENT"> INITIAL_EXTENT <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="NEXT_EXTENT"> NEXT_EXTENT <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="MIN_EXTENTS"> MIN_EXTENTS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="MAX_EXTENTS"> MAX_EXTENTS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="PCT_INCREASE"> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/186-191.html (2 of 5)4/03/2005 6:15:44<br />
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PCT_INCREASE <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="FREELISTS"> FREELISTS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="FREELIST_GROUPS"> FREELIST_GROUPS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="BACKED_UP"> BACKED_UP <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="NUM_ROWS"> NUM_ROWS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="BLOCKS"> BLOCKS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="EMPTY_BLOCKS"> EMPTY_BLOCKS <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="AVG_SPACE"> AVG_SPACE <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="CHAIN_CNT"> CHAIN_CNT <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="AVG_ROW_LEN"> AVG_ROW_LEN <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="DEGREE"> DEGREE <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="INSTANCES"> INSTANCES <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="CACHE"> CACHE <BR> <INPUT TYPE="checkbox" NAME="COLS" VALUE="TABLE_LOCK"> TABLE_LOCK <BR> <INPUT TYPE="submit" VALUE="Execute Query"> </FORM> </BODY> </HTML> Figure 7.5 depicts the Web page using htp.formCheckbox.<br />
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Figure 7.5 A sample Web page using htp.formCheckbox.<br />
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htp.formClose The htp.formClose hypertext procedure closes an HTML form. Forms are opened by the htp. formOpen procedure. There are no parameters for this procedure.<br />
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Note: See procedure htp.formSelectOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.formHidden The htp.formHidden hypertext procedure sends a field value with a form. However, the user will not see the value as part of the transmission. Parameters: cname(in), cvalue(in), cattributes(in) • cname—Defines the internal reference name for the contents of the field (varchar2). • cvalue—Assigns the value of the field (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.formCheckbox for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.formImage The htp.formImage hypertext procedure posts an image that can be clicked on to submit a form. Parameters: cname(in), csrc(in), calign(in), cattributes(in) • • • •<br />
<br />
cname—Creates an internal reference name for the image (varchar2). csrc—Indicates the actual image file name (varchar2). calign—Defines the placement for the image on the Web page (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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Creating an image map is accomplished by using a combination of the formImage and formOpen hypertext procedures. As you can see in Listing 7.11, the formImage procedure parameters include the internal name of the image (BobPic), and the actual image file (papaj.gif, which, in this case, happens to be me). Now, you also need the formOpen procedure to tell the Web Listener where you are transferring to based on where you clicked on the image. The hotspots on the image are defined by X and Y coordinates. This cumbersome task of defining hotspots on image maps was discussed in the CGI chapter. When you click on a specific X,Y coordinate on an image, three parameters are passed to the URL identified in the formOpen procedure. The URL in Listing 7.11 is the procedure called ‘s00’, which must be set up to receive the three parameters, including the internal image name, the X coordinate, and the Y coordinate. So, if you click on Bob’s nose, you go to one URL, and if you click on Bob’s ear, you go to another location. For another perspective on the relationship between the formOpen and formImage procedures, see the htp.formOpen definition.<br />
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Listing 7.11 displays a PL/SQL code example using the htp.formImage procedure, and Listing 7.12 shows the HTML code generated by this procedure. Listing 7.11 PL/SQL code using htp.formImage. create or replace procedure formimage as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formImage'); htp.header(1,'Oracle WebServer htp.formImage Examples'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's00'); htp.print('Click on the Image to submit Form'); htp.formImage('BobPic','/ows-img/papaj.gif'); htp.nl; htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.12 HTML code using htp.formImage. <HTML> <HEAD> <TITLE>Oracle Webserver formImage</TITLE> <H1>Oracle WebServer htp.formImage Examples</H1><br />
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</HEAD> <BODY> <FORM ACTION="/ows-bin/owa/s00" METHOD="POST"> Click on the Image to submit Form <INPUT TYPE="image" NAME="BobPic" SRC="/ows-img/papaj.gif"> <BR> </FORM> </BODY> </HTML> Figure 7.6 depicts the Web page using htp.formImage.<br />
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Figure 7.6 A sample Web page using htp.formImage.<br />
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htp.formOpen The htp.formOpen hypertext procedure specifies the name of the procedure that will be invoked when a form is submitted. Generally, a form is submitted using htp.formSubmit or htp.formImage. The formOpen is always used in combination with either formSubmit or formImage. Parameters: curl(in), cmethod(in), ctarget(in), cenctype(in), cattributes(in) • curl—This is the URL identifying the executable script (e.g., CGI) that will generate the form (varchar2). • cmethod—This is the method used to transfer data to and from the form (varchar2). Default POST. The other option is GET. • ctarget—This parameter should be left blank (varchar2). • cenctype—This is the encryption type for the data being transferred (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. For example, this pair will create a push button, which, when clicked, will create the Web page defined in the stored procedure called destination_page_name : htp.formOpen(owa_util_.get_owa_service_path||'destination_page_name'); htp.formSubmit(NULL, 'Press here to transfer to destination Web page');<br />
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Note: Normally a stored procedure name is used with htp.formSubmit, but here NULL is used, so the stored procedure specified by htp.formOpen is used.<br />
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In this example, a form image will be created which, when clicked, will create the Web page that is defined in the stored procedure called destination_page_name : htp.formOpen(owa_util_.get_owa_service_path||'destination_page_name'); htp.formImage('internal_image_name','actual_image_file_name'); htp.formImage will pass three parameters to destination_procedure_name. It will pass internal_image_name internal_image_name.x internal_image_name.y<br />
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varchar2; int; int;<br />
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where x is the X pixel coordinate and y is the Y pixel coordinate. These coordinates are used by the<br />
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receiving page to interrogate the pixel coordinates and transfer to other functions. Therefore, in this case, destination_procedure_name would need to be defined with these three input parameters. Here is the prototype: destination_procedure_name(internal_image_in in varchar2, internal_image_in.x in int, internal_image_in.y in int);<br />
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htp.formPassword The htp.formPassword hypertext procedure creates a protected data entry field. Parameters: cname(in), csize(in), cmaxlength(in), cvalue(in), cattributes(in) • cname—Defines the internal reference name for the contents of the field (varchar2). • csize—Defines the displayed number of characters (varchar2). • cmaxlength—Defines the maximum number of characters that the field can contain (varchar2). Default NULL. • cvalue—Defines the value associated with the password (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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Note: A text field with csize=5 and cmaxlength=10 will only display 5 characters, but it will be able to accept 10 characters. In this case, you may enter 10 characters, and use the arrow keys to display the entire text string.<br />
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Listing 7.13 displays a PL/SQL code example using the htp.form Password procedure, and Listing 7.14 shows the HTML code generated by this procedure. Listing 7.13 PL/SQL code using htp.formPassword. create or replace procedure formpassword as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formPassword'); htp.header(1,'Oracle WebServer htp.formPassword Examples'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 'formpassword'); htp.print('ENTER Userid: '); htp.formText('Userid',10,50); htp.nl; htp.print('ENTER Password: '); htp.formPassword('Password',10,50); htp.nl; htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.14 HTML code using htp.formPassword. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/191-195.html (3 of 4)4/03/2005 6:15:45<br />
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<HTML> <HEAD> <TITLE>Oracle Webserver formPassword</TITLE> <H1>Oracle WebServer htp.formPassword Examples</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/formpassword" METHOD="POST"> ENTER Userid: <INPUT TYPE="text" NAME="Userid" SIZE="10" MAXLENGTH="50"> <BR> ENTER Password: <INPUT TYPE="password" NAME="Password" SIZE="10" MAXLENGTH="50"> <BR> </FORM> </BODY> </HTML> Figure 7.7 depicts the Web page using htp.formPassword.<br />
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Figure 7.7 A sample Web page using htp.formPassword.<br />
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htp.formRadio The htp.formRadio hypertext procedure inserts a radio button into an HTML form. Parameters: cname(in), cvalue(in), cchecked(in), cattributes(in) • cname—Defines the internal reference name for the contents of the field (varchar2). Each radio button should have the same name because you can only select one. • cvalue—Assigns the value associated with this button (varchar2). For example, one radio button might have the value “Visa” and another “Amex”. • cchecked—Indicates that the button default is “checked” (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.15 displays a PL/SQL code example using the htp.formRadio procedure, and Listing 7.16 shows the HTML code generated by this procedure. Listing 7.15 PL/SQL code using htp.formRadio. create or replace procedure formradio is cursor cols is select nationality from nations order by nationality ; BEGIN<br />
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htp.htmlOpen; htp.headOpen; htp.htitle('Choose a nationality.'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path||'formradio'); htp.formHidden('COLS', 'dummy'); for crec in cols loop htp.formRadio('COLS',crec.nationality); htp.print(crec.nationality); htp.nl; end loop; htp.formSubmit(NULL, 'Execute Query'); htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.16 HTML code using htp.formRadio. <HTML> <HEAD> <TITLE>Choose a nationality.</TITLE> <H1>Choose a nationality.</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/formradio" METHOD="POST"> <INPUT TYPE="hidden" NAME="COLS" VALUE="dummy"> <INPUT TYPE="radio" NAME="COLS" VALUE="Bosnia"> Bosnia <BR> <INPUT TYPE="radio" NAME="COLS" VALUE="Finnish"> Finnish <BR> <INPUT TYPE="radio" NAME="COLS" VALUE="Slobovia"> Slobovia <BR> <INPUT TYPE="radio" NAME="COLS" VALUE="USA"> USA <BR> <INPUT TYPE="submit" VALUE="Execute Query"> </FORM> </BODY> </HTML> Figure 7.8 depicts the Web page using htp.formRadio.<br />
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Figure 7.8 A sample Web page using htp.formRadio.<br />
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htp.formReset The htp.formReset hypertext procedure inserts a Reset button into an HTML form, which can be used to reset all the input data fields to their original values. Parameters: cvalue(in), cattributes(in) • cvalue—Defines the value associated with the button (varchar2). Defaults to Reset. • cattributes—Settings to define the HTML tag attributes (varchar2). Default NULL. Listing 7.17 displays a PL/SQL code example using the htp.formReset procedure, and Listing 7.18 shows the HTML code generated by this procedure. Listing 7.17 PL/SQL code using htp.formReset. create or replace procedure formreset as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formReset'); htp.header(1,'Oracle WebServer htp.formReset Examples'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 'formreset'); htp.print('Server Name: '); htp.formText('Server Name',10,50); htp.nl; htp.print('Instance Name: '); htp.formText('Instance Name',10,50); htp.nl; htp.formReset; htp.nl; htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.18 HTML code using htp.formReset. <HTML> <HEAD> <TITLE>Oracle Webserver formReset</TITLE> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/195-200.html (3 of 5)4/03/2005 6:15:46<br />
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<H1>Oracle WebServer htp.formReset Examples</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/formreset" METHOD="POST"> Server Name: <INPUT TYPE="text" NAME="Server Name" SIZE="10" MAXLENGTH="50"> <BR> Instance Name: <INPUT TYPE="text" NAME="Instance Name" SIZE="10" MAXLENGTH="50"> <BR> <INPUT TYPE="reset" VALUE="Reset"> <BR> </FORM> </BODY> </HTML> Figure 7.9 depicts the Web page using htp.formReset.<br />
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Figure 7.9 A sample Web page using htp.formReset.<br />
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htp.formSelectClose The htp.formSelectClose hypertext procedure ends a list of selections. This HTML section is opened by the htp.formSelectOpen procedure. There are no parameters for this procedure.<br />
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Note: See procedure htp.formSelectOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.formSelectOpen The htp.formSelectOpen hypertext procedure begins a list of alternatives to select. Parameters: cname(in), cprompt(in), nsize(in), cattributes(in) • cname—Defines the internal reference name for the selection (varchar2). • cprompt—Creates a text prompt on the form for the selections(varchar2). Default NULL. • nsize—Determines the number of selections on the form (integer). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.19 displays a PL/SQL code example using the htp.formSelectOpen procedure, and Listing 7.20 shows the HTML code generated by this procedure. Listing 7.19 PL/SQL code using htp.formSelectOpen. create or replace procedure formselectopen as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formSelectOpen'); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/195-200.html (4 of 5)4/03/2005 6:15:46<br />
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htp.header(1,'Oracle WebServer htp.formSelectOpen Examples'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 'test'); htp.formSelectOpen('input_var_name:','Choose the Server Site:'); htp.nl; htp.nl; htp.formSelectOption('Buffalo'); htp.nl; htp.formSelectOption('Rochester'); htp.nl; htp.formSelectOption('Syracuse'); htp.nl; htp.formSelectClose; htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors<br />
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Listing 7.20 HTML code using htp.formSelectOpen. <HTML> <HEAD> <TITLE>Oracle Webserver formSelectOpen</TITLE> <H1>Oracle WebServer htp.formSelectOpen Examples</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/test" METHOD="POST"> Choose the Server Site:<SELECT NAME="input_var_name:"> <BR> <BR> <OPTION>Buffalo <BR> <OPTION>Rochester <BR> <OPTION>Syracuse <BR> </SELECT> </FORM> </BODY> </HTML> Figure 7.10 depicts the Web page using htp.formSelectOpen.<br />
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Figure 7.10 A sample Web page using htp.formSelectOpen.<br />
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Note: Rather than hard-coding the pop-up values in the form, you can retrieve the values from your Oracle database and dynamically create a Web page with the database values. To see how to dynamically generate pop-up lists, see Chapter 10.<br />
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htp.formSelectOption The htp.formSelectOption hypertext procedure represents one selection from a list. This list is displayed within the context of an HTML form. Parameters: cvalue(in), cselected(in), cattributes(in) • cvalue—Defines the displayed selection (varchar2). • cselected—Does nothing. Default NULL. • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.formSelectOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.formSubmit The htp.formSubmit hypertext procedure creates a button used to submit a form. Parameters: cname(in), cvalue(in), cattributes(in) • cname—Defines the internal reference name for the form (varchar2). Default NULL. • cvalue—Identifies the button as one being used for submitting forms (varchar2). Default Submit. • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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Note: See procedure htp.formRadio for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.formText The htp.formText function creates an input field for textual data entry and updates. Parameters: cname(in), csize(in), cmaxlength(in), cvalue(in), cattributes(in) file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/201-205.html (2 of 5)4/03/2005 6:15:46<br />
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• cname—Defines the internal reference name for the contents of the field (varchar2). • csize—Assigns the displayed number of characters in the field (varchar2). Default NULL. • cmaxlength—Defines the maximum number of characters that the field can contain (varchar2). Default NULL. • cvalue—Indicates the default text within the field (varchar2). Default NULL. • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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Note: A text field with csize=5 and cmaxlength=10 will only display 5 characters, but will be able to accept 10 characters. In this case, you may enter 10 characters, and use the arrow keys to display the entire text string.<br />
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Listing 7.21 displays a PL/SQL code example using the htp.formText procedure, and Listing 7.22 shows the HTML code generated by this procedure. Listing 7.21 PL/SQL code using htp.formText. create or replace procedure formtext as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formText'); htp.header(1,'Oracle WebServer htp.formText Examples'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 'formtext'); htp.print('Size 1: '); htp.formText('U',10,50); htp.nl; htp.print('Size 10: '); htp.formText('V',10,50); htp.nl; htp.print('Size 20: '); htp.formText('W',20,50); htp.nl; htp.print('Size 30: '); htp.formText('X',30,50); htp.nl; htp.print('Size 40: '); htp.formText('Y',40,50,'This is a default value'); htp.nl;<br />
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htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.22 HTML code using htp.formText. <HTML> <HEAD> <TITLE>Oracle Webserver formText</TITLE> <H1>Oracle WebServer htp.formText Examples</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/formtext" METHOD="POST"> Size 1: <INPUT TYPE="text" NAME="U" SIZE="10" MAXLENGTH="50"> <BR> Size 10: <INPUT TYPE="text" NAME="V" SIZE="10" MAXLENGTH="50"> <BR> Size 20: <INPUT TYPE="text" NAME="W" SIZE="20" MAXLENGTH="50"> <BR> Size 30: <INPUT TYPE="text" NAME="X" SIZE="30" MAXLENGTH="50"> <BR> Size 40: <INPUT TYPE="text" NAME="Y" SIZE="40" MAXLENGTH="50" VALUE="This is a default value"> <BR> </FORM> </BODY> </HTML> Figure 7.11 depicts the Web page using htp.formText.<br />
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Figure 7.11 A sample Web page using htp.formText.<br />
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htp.formTextarea The htp.formTextarea hypertext procedure creates a text area that does not have any predefined text. This procedure enables a user to enter text into the text field. Parameters: cname(in), nrows(in), ncols(in), calign(in), cattributes(in)<br />
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• • • • •<br />
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cname—Names the text field (varchar2). nrows—Defines the number of rows in the text field (integer). ncols—Defines the number of text columns (integer). calign—Sets the text input alignment (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.formTextarea2 The htp.formTextarea2 hypertext procedure creates a text area that does not have any predefined text and allows text to be entered by a user into the text field. However, this procedure is different from htp.formTextarea in that it allows for a wrap style for the text. Parameters: cname(in), nrows(in), ncols(in), calign(in), cwrap(in), cattributes(in) • • • • • •<br />
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cname—Names the text field (varchar2). nrows—Defines the number of rows in the text field (integer). ncols—Defines the number of text columns (integer). calign—Sets the text input alignment (varchar2). Default NULL. cwrap—Specifies a text wrap style (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.formTextareaClose The htp.formTextareaClose hypertext procedure ends a text area field defined with procedure htp.formTextarea. There are no parameters necessary for this procedure.<br />
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htp.formTextareaClose2 The htp.formTextareaClose2 hypertext procedure ends a text area field defined with file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/205-208.html (1 of 3)4/03/2005 6:15:47<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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procedure htp.formTextarea2. There are no parameters associated with this procedure.<br />
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htp.formTextareaOpen The htp.formTextareaOpen hypertext procedure begins a text area (section defined for text). Within this text area, predefined text can be inserted. Parameters: cname(in), nrows(in), ncols(in), calign(in), cattributes(in) • • • • •<br />
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cname—Names the text area (varchar2). nrows—Defines the number of rows in the text area (integer). ncols—Defines the number of text columns (integer). calign—Sets the text input alignment (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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formTextareaOpen2 The formTextareaOpen2 hypertext procedure begins a text area with predefined text. The predefined text will always be displayed in the text field. This procedure allows for the specification of a wrap style for the text. Parameters: cname(in), nrows(in), ncols(in), calign(in), cwrap(in), cattributes(in) • • • • • •<br />
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cname—Names the text area (varchar2). nrows—Defines the number of rows in the text area (integer). ncols—Defines the number of text columns (integer). calign—Sets the text input alignment (varchar2). Default NULL. cwrap—Sets the text wrapping style (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.frame The htp.frame hypertext procedure generates an HTML tag that defines a frame. A frame is a way of separating data or functions into different windows within a Web page, thus enabling distinct processing to occur within partitioned sections of the document. Parameters: csrc(in), cname(in), cmarginwidth(in), cmarginheight(in), cscrolling(in), cnoresize(in), cattributes(in) • csrc—Names the object to be sourced within the frame (varchar2). • cname—Defines the internal name of the frame (varchar2). Default NULL. • cmarginwidth—Defines the width of the frame (varchar2). Default NULL. • cmarginheight—Defines the height of the frame (varchar2). Default NULL. • cscrolling—Defines scrolling for the frame (varchar2). Default NULL. • cnoresize—Defines no-resizing for this frame (varchar2). Default NULL. • cattributes—Settings for the HTML tag attributes (varchar2). Default NULL.<br />
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htp.framesetClose The htp.framesetClose hypertext procedure generates an HTML tag to end a group of frames within a Web page. This group of frames was opened by the htp. framesetOpen procedure. There are no parameters related to this hypertext procedure.<br />
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htp.framesetOpen The htp.framesetOpen hypertext procedure begins a set of frames within a Web page. There are no required parameters associated with this procedure. Parameters: crows(in), ccols(in), cattributes(in) • crows—Defines the number of rows for the frame (varchar2). Default NULL. • ccols—Defines the number of columns for the frame (varchar2). Default NULL. • cattributes—Settings for the HTML tag attributes (varchar2). Default NULL.<br />
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htp.headClose The htp.headClose hypertext procedure specifies the end of the head in the HTML document. There are no parameters associated with this procedure. The HTML head is opened by hypertext procedure htp.headOpen.<br />
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htp.header The htp.header hypertext procedure defines your HTML document headings. You’ll notice that different levels defined for headers represent different font sizes. Parameters: nsize(in), cheader(in), calign(in), cnowrap(in), cclear(in), cattributes(in) • nsize—Determines the header levels; 1 through 6 (integer).<br />
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• • • • •<br />
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cheader—Indicates the text of the header (varchar2). calign—Aligns the heading (varchar2). Default NULL. cnowrap—Indicates to display the heading without wrapping (varchar2). Default NULL. cclear—Indicates to insert a new line with the heading (varchar2). Default NULL. cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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Listing 7.23 displays a PL/SQL code example using the htp.header procedure, and Listing 7.24 shows the HTML code generated by this procedure. Listing 7.23 PL/SQL code using htp.header. create or replace procedure header as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle htp.header(2,'Oracle htp.header(3,'Oracle htp.header(4,'Oracle htp.header(5,'Oracle htp.header(6,'Oracle htp.headClose; htp.bodyOpen;<br />
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WebServer WebServer WebServer WebServer WebServer WebServer<br />
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htp.header htp.header htp.header htp.header htp.header htp.header<br />
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htp.nl; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.24 HTML code using htp.header. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/208-213.html (2 of 7)4/03/2005 6:15:48<br />
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Example'); Example'); Example'); Example'); Example'); Example');<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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<HTML> <HEAD> <H1>Oracle <H2>Oracle <H3>Oracle <H4>Oracle <H5>Oracle <H6>Oracle </HEAD> <BODY> <BR> </BODY> </HTML><br />
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WebServer WebServer WebServer WebServer WebServer WebServer<br />
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htp.header htp.header htp.header htp.header htp.header htp.header<br />
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Example</H1> Example</H2> Example</H3> Example</H4> Example</H5> Example</H6><br />
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Figure 7.12 depicts the Web page using htp.header.<br />
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Figure 7.12 A sample Web page using htp.header.<br />
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htp.headOpen The htp.headOpen hypertext procedure specifies the beginning of an HTML document head. There are no input or output parameters for this procedure.<br />
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htp.hr The htp.hr hypertext procedure is an alias for procedure htp.line. The htp.line procedure creates a line within the HTML document.<br />
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htp.htmlClose file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/208-213.html (3 of 7)4/03/2005 6:15:48<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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The htp.htmlClose hypertext procedure specifies the end of your HTML code. This procedure has no parameters associated with it. The HTML document is opened with procedure htp.htmlOpen.<br />
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htp.htmlOpen The htp.htmlOpen hypertext procedure specifies the beginning of your HTML code. There are no input or output parameters related to this procedure.<br />
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htp.img The htp.img hypertext procedure displays images on a Web page. In addition, coding can be added to make the image function as a push button or to map different parts of the image to different responses. Parameters: curl(in), calign(in), calt(in), cismap(in), cattributes(in) • curl—Identifies the URL of the image to be loaded (varchar2). Default NULL. • calign—Aligns image (varchar2). Default NULL. • calt—Creates a hypertext line, which is displayed while the image is being loaded (varchar2). Some Web browsers cannot display images, which would make this hypertext line all the more important. Default NULL. • cismap—Specifies that this image is an image map (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.25 displays a PL/SQL code example using the htp.img procedure, and Listing 7.26 shows the HTML code generated by this procedure. Listing 7.25 PL/SQL code using htp.img. create or replace procedure img as begin htp.htmlOpen; htp.headOpen; htp.title('img'); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/208-213.html (4 of 7)4/03/2005 6:15:48<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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htp.header(1,'Oracle WebServer'); htp.header(1,'Image Example'); htp.headClose; htp.bodyOpen; htp.nl; htp.nl; htp.img('/ows-img/iconmngr.gif'); htp.nl; htp.p('This is a static Image'); htp.nl; htp.nl; htp.nl; htp.anchor('/ows-bin/owa/s10',htf.img('/ows-img/burleson.gif','','','', 'HEIGHT=100, WIDTH=120 <BR> <H1> Click on Don to go to procedure s10 </H1>')); htp.anchor('/ows-bin/owa/s20',htf.img('/ows-img/papaj.gif','','', 'ISMAP','HEIGHT=100, WIDTH=120 <BR> <H1> Bob is an image map, and procedure s20 will receive the map coordinates </H1>')); htp.bodyClose; htp.htmlClose; end; / show errors Note that the first static image call (htp.img) is very straightforward, but it is not clear where the image is being loaded from. In this case, the call htp.img(‘/ows-img/iconmngr.gif’), tells the WebServer to load iconmngr.gif from the directory specified in the WebServer Listener Administration—Directory Mappings—with the virtual directory ‘/owsimg’ (see Figure 7.13). file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/208-213.html (5 of 7)4/03/2005 6:15:48<br />
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Figure 7.13 The Directory Mappings page within WebServer Listener Administration. Listing 7.26 HTML code using htp.img. <HTML> <HEAD> <TITLE>img</TITLE> <H1>Oracle WebServer</H1> <H1>Image Example</H1> </HEAD> <BODY> <BR> <BR> <IMG SRC="/ows-img/iconmngr.gif"> <BR> This is a static Image <BR> <BR> <BR> <A HREF="/ows-bin/owa/s10" rel="nofollow"><IMG SRC="/ows-img/burleson.gif" HEIGHT=100, WIDTH=120 <BR> <H1> Click on Don to go to procedure s10 </H1>></A> <A HREF="/ows-bin/owa/s20" rel="nofollow"><IMG SRC="/ows-img/papaj.gif" ISMAP HEIGHT=100, WIDTH=120 <BR> <H1> Bob is an image map, and procedure s20 will receive the map coordinates </H1>></A> </BODY> </HTML> Figure 7.14 depicts the Web page using htp.img.<br />
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Figure 7.14 A sample Web page using htp.img.<br />
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htp.img2 The htp.img2 hypertext procedure loads an image into a Web page. You will notice that there can be alternate hypertext displayed with the image. This procedure can source an image from the client site. That is, the map file for the image map is stored within the HTML document, which allows for all processing to occur locally. The map file contains the link and region instructions for the image map.<br />
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Note: Your Web browser needs to be client-side compatible to use the htp.img2 procedure. The current versions of Netscape and Internet Explorer are compatible.<br />
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Parameters: curl(in), calign(in), calt(in), cismap(in), cusemap(in), cattributes(in) • curl—Indicates the URL of the image to be loaded (varchar2). Default NULL. • calign—Sets the image alignment (varchar2). Default NULL. • calt—Creates a hypertext line, which is displayed while the image is being loaded (varchar2). Some Web browsers cannot display images, which would make this hypertext line all the more important. This hypertext line is also useful when loading the image takes a long period of time. Default NULL. • cismap—Specifies that this image is an image map (varchar2). Default NULL. • cusemap—Specifies an image sourced from the client site (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.isindex The htp.isindex hypertext procedure generates an HTML tag that sends text as a prompt to a URL site. Usually, a program or Web page will receive this information. Parameters: cprompt(in), curl(in) • cprompt—Identifies the text sent as a prompt (varchar2). Default NULL. • curl—Identifies the program or Web page to be received in response to the prompt message file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/213-217.html (1 of 4)4/03/2005 6:15:48<br />
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(varchar2). Default NULL.<br />
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htp.italic The htp.italic hypertext procedure places italicized text on a Web page. This type of highlighting is an effective feature for clarifying the information presented. You will notice in this example two ways to italicize text. One is by using the htp.italic procedure as a standalone process. The second is to embed this procedure as a hypertext function within the htp.print procedure. Parameters: ctext(in), cattributes(in) • ctext—Indicates the text to be italicized (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.27 displays a PL/SQL code example using the htp.italic procedure, and Listing 7.28 shows the HTML code generated by this procedure. Listing 7.27 PL/SQL code using htp.italic. create or replace procedure italic as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.italic Example'); htp.headClose; htp.bodyOpen; htp.nl; htp.italic('This is italicized TEXT'); htp.nl; htp.print(htf.italic('Printed Italics')); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.28 HTML code using htp.italic. <HTML> <HEAD> <H1>Oracle WebServer htp.italic Example</H1> </HEAD> <BODY> <BR> <I>This is italicized TEXT</I> <BR> <I>Printed Italics</I> </BODY> </HTML> Figure 7.15 depicts the Web page using htp.italic.<br />
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Figure 7.15 A sample Web page using htp.italic.<br />
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htp.kbd The htp.kbd hypertext procedure is an alias for the htp.keyboard procedure. The procedure will display text in monospace, as it would be entered by a user.<br />
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Note: See procedure htp.keyboard for examples of PL/SQL and HTML code related to this procedure.<br />
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htp.keyboard The htp.keyboard hypertext procedure displays text as if it were entered by a user. This means that all the characters are displayed in monospace typeface. Parameters: ctext(in), cattributes(in) • ctext—Indicates the text to be displayed (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.29 displays a PL/SQL code example using the htp.keyboard procedure, and Listing 7.30 shows the HTML code generated by this procedure. Listing 7.29 PL/SQL code using htp.keyboard. create or replace procedure keyboard as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.keyboard Example'); htp.headClose; htp.bodyOpen; htp.nl; htp.keyboard('A media failure occurred at 12 midnight.'); htp.nl; htp.keyboard('After replacing the disk and restoring the OS files,'); htp.nl; htp.kbd('we did a point-in-time recovery.'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.30 HTML code using htp.keyboard. <HTML> <HEAD> <H1>Oracle WebServer htp.keyboard Example</H1> </HEAD> <BODY> <BR> <KBD>A media failure occurred at 12 midnight.</KBD> <BR> <KBD>After replacing the disk and restoring the OS files,</KBD> <BR> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/213-217.html (3 of 4)4/03/2005 6:15:48<br />
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<KBD>we did a point-in-time recovery.</KBD> </BODY> </HTML> Figure 7.16 depicts the Web page using htp.keyboard.<br />
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Figure 7.16 A sample Web page using htp.keyboard.<br />
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htp.line The htp.line hypertext procedure generates an HTML tag that creates lines within a Web page. This feature can be used to better separate information on a document. Parameters: cclear(in), csrc(in), cattributes(in) • cclear—Inserts a new line into the document (varchar2). Default NULL. • csrc—Specifies an image as the source of the line (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.31 displays a PL/SQL code example using the htp.line procedure, and Listing 7.32 shows the HTML code generated by this procedure. Listing 7.31 PL/SQL code using htp.line. create or replace procedure line as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.line Example'); htp.headClose; htp.bodyOpen; htp.nl; htp.line; htp.print('This text appears between the lines'); htp.line;<br />
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htp.nl; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.32 HTML code using htp.line. <HTML> <HEAD> <H1>Oracle WebServer htp.line Example</H1> </HEAD> <BODY> <BR> <HR> This text appears between the lines <HR> <BR> </BODY> </HTML> Figure 7.17 depicts the Web page using htp.line.<br />
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Figure 7.17 A sample Web page using htp.line.<br />
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htp.linkRel The htp.linkRel hypertext procedure generates an HTML tag that describes the relationship of a hyperlink between an htp.anchor procedure and the target URL. Essentially, this is the next link within this document. The htp.anchor procedure actually creates the hyperlink and must use the HREF attribute for the htp.linkRel procedure to function correctly. Parameters: crel(in), curl(in), ctitle(in) • crel—Defines the relationship between htp.anchor and the target URL (varchar2). Default NULL. • curl—Identifies the target URL (varchar2). • ctitle—Defines the title given to the relationship (varchar2). Default NULL.<br />
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htp.linkRev The htp.linkRev hypertext procedure is the reverse of the procedure htp.linkRel and describes the relationship of the hyperlink from the target to the htp.anchor point. This basically is the previous link within this document. The hyperlink is actually created by the htp.anchor procedure, not htp.linkRev. Parameters: crev(in), curl(in), ctitle(in)<br />
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• crev—Defines the relationship between the target URL and the htp.anchor point (varchar2). Default NULL. • curl—Identifies the target URL (varchar2). • ctitle—Defines the title given to the relationship (varchar2). Default NULL.<br />
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htp.listHeader The htp.listHeader hypertext procedure generates an HTML tag to create a heading for an item list. The procedure call to htp.listHeader precedes the call to procedure htp.listItem. Parameters: ctext(in), cattributes(in) • ctext—Identifies the text displayed in the header (varchar2). • cattributes—Settings for HTML tag attributes (varchar2). Default NULL.<br />
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Note: See procedure htp.dirlistOpen for examples of PL/SQL and HTML code related to this procedure.<br />
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htp.listingClose The htp.listingClose hypertext procedure creates an HTML tag that ends a listing of fixedwidth text. There are no parameters associated with this procedure.<br />
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Note: See procedure htp.listingOpen for examples of PL/SQL and HTML code related to this procedure.<br />
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htp.listingOpen The htp.listingOpen hypertext procedure creates a listing with fixed-width text. It is used in conjunction with the htp.listItem procedure to produce the listing. There are no parameters for this procedure. Listing 7.33 displays a PL/SQL code example using the htp.listingOpen procedure, and Listing 7.34 shows the HTML code generated by this procedure. Listing 7.33 PL/SQL code using htp.listingOpen. create or replace procedure listing as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.listingOpen Example'); htp.headClose; htp.bodyOpen; htp.nl; htp.listingOpen; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/217-222.html (3 of 5)4/03/2005 6:15:49<br />
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htp.listItem('Reorg the data by exporting the tables in compressed mode,'); htp.listItem('dropping the tables, then importing the data and structures'); htp.listItem('into one extent.'); htp.listingClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.34 HTML code using htp.listingOpen. <HTML> <HEAD> <H1>Oracle WebServer htp.listingOpen Example</H1> </HEAD> <BODY> <BR> <LISTING> <LI>Reorg the data by exporting the tables in compressed mode, <LI>dropping the tables, then importing the data and structures <LI>into one extent. </LISTING> </BODY> </HTML> Figure 7.18 depicts the Web page using htp.listingOpen.<br />
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Figure 7.18 A sample Web page using htp.listingOpen.<br />
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htp.listItem The htp.listItem hypertext procedure produces an HTML tag that will enable the formatting of an item. These items will comprise a listing created to your specifications. Parameters: ctext(in), cclear(in), cparm(in), csrc(in), cattributes(in) • ctext—Identifies the text displayed in the item (varchar2). Default NULL. • cclear—Determines if a new line is inserted into the document (varchar2). Default NULL. • cparm—Carries no purpose(varchar2). Default NULL. • csrc—Identifies a file that can be sourced (varchar2). Default NULL. • cattributes—Settings for HTML tag attributes (varchar2). Default NULL.<br />
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Note: See procedure htp.dirlistOpen for examples of the PL/SQL and HTML code related to this procedure. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/217-222.html (4 of 5)4/03/2005 6:15:49<br />
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htp.mailto The htp.mailto hypertext procedure concatenates the mailto identifier to the front of the address of the anchor. This is useful for sending mail messages to an email address. When the message is received, the recipient can click on the hypertext to open a dialog box with the subject and body of the message and then respond as necessary. Most, but not all, Web browsers are compatible with the mailto protocol. Parameters: caddress(in), ctext(in), cname(in), cattributes(in) • caddress—Identifies the address to receive the mail (varchar2). • ctext—Identifies the hypertext sent with the message that the receiver can click on to open a dialog box (varchar2). • cname—Identifies the name associated with the mail message (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. For example, the HREF attribute generated from this procedure would be formatted like: HREF="mailto:caddress" An example of the htp.mailto procedure could look like: htp.mailto('billclinton@whitehouse.org','Hello to the President');<br />
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htp.mapClose The htp.mapClose hypertext procedure generates an HTML tag to close the specification for a client-side image map. The definition for this image map is opened by the procedure htp. mapOpen. There are no input or output parameters related to this procedure.<br />
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htp.mapOpen<br />
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The htp.mapOpen hypertext procedure begins the definition of an image map sourced from the client site. Client-side image maps store map files within an HTML document, so all processing of the HTML document is local. These files contain the link and region instructions for the document. Parameters: cname(in), cattributes(in) • cname—Defines the internal name of the image map (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.menulistClose The htp.menulistClose hypertext procedure closes a menu list. There are no parameters associated with this procedure. A menu list is opened by the hypertext procedure htp. menulistOpen.<br />
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Note: See procedure htp.menulistOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.menulistOpen The htp.menulistOpen hypertext procedure begins a menu list on a Web page, which is displayed as a compact bullet list. There are no input or output parameters related to this procedure. A menu list is closed by using the hypertext procedure htp.menulistClose. There are no parameters associated with this procedure. Listing 7.35 displays a PL/SQL code example using the htp.menulistOpen procedure, and Listing 7.36 shows the HTML code generated by this procedure. Listing 7.35 PL/SQL code using htp.menulistOpen. create or replace procedure menulist as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.menulist Example'); htp.headClose; htp.bodyOpen; htp.menulistOpen; htp.listHeader('Server Information'); htp.listItem('Item 1: Hostname: Spartan'); htp.listItem('Item 2: OS: Solaris 2.5'); htp.listItem('Item 3: #CPUs: 4'); htp.listItem('Item 4: RAM: 256mb'); htp.menulistClose; htp.bodyClose; htp.htmlClose; end; /<br />
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show errors Listing 7.36 HTML code using htp.menulistOpen. <HTML> <HEAD> <H1>Oracle WebServer htp.menulist Example</H1> </HEAD> <BODY> <MENU> <LH>Server Information</LH> <LI>Item 1: Hostname: Spartan <LI>Item 2: OS: Solaris 2.5 <LI>Item 3: #CPUs: 4 <LI>Item 4: RAM: 256mb </MENU> </BODY> </HTML> Figure 7.19 depicts the Web page using htp.menulistOpen.<br />
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Figure 7.19 A sample Web page using htp.menulistOpen.<br />
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htp.meta The htp.meta hypertext procedure sends metadata to the Web browser about information being transferred to it. This information helps to identify what is being returned to assist in determining the disposition of the feed. Parameters: chttp_equiv(in), cname(in), ccontent(in) • chttp_equiv—Supplies a description of the feed (varchar2). • cname—Defines the internal name for this transmission (varchar2). • ccontent—Setting to specify input for this function (varchar2). In this example, the current URL is refreshed (or reloaded) automatically every 60 seconds: htp.meta ('Refresh', NULL, 60); Here is the HTML code generated from this procedure: <META HTTP-EQUIV="Refresh" NAME="" CONTENT="60"><br />
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htp.nl The htp.nl hypertext procedure inserts a new line into the HTML document. This helps space out the items on a Web page to improve the clarity of the presentation. There are no parameters associated with this procedure.<br />
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htp.nobr<br />
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The htp.nobr hypertext procedure marks a section of text within a Web document as not containing line breaks. This will be useful for displaying text more compactly. Parameters: ctext(in) • ctext—Defines text as not having line breaks (varchar2).<br />
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htp.noframesClose The htp.noframesClose hypertext procedure ends a set of frame-like content to be displayed within an HTML document by a Web browser that cannot process frames. This set of frame-like content is opened by the htp.noframesOpen procedure. There are no parameters associated with this hypertext procedure.<br />
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htp.noframesOpen The htp.noframesOpen hypertext procedure generates an HTML tag that opens a set of framelike content within a Web browser that cannot display frames. There are no parameters related to this procedure.<br />
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htp.olistClose The htp.olistClose hypertext procedure creates an HTML tag to end an ordered list of items. Using ordered lists can be a good presentation aid for a Web page by allowing numbered identification of items. There are no parameters associated with this procedure.<br />
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Note: See procedure htp.olistOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.olistOpen The htp.olistOpen hypertext procedure creates an HTML tag that opens a list of items that are ordered. Notice in Listing 7.37 that numbers are automatically generated for each item in the listing. Parameters: cclear(in), cwrap(in), cattributes(in) • cclear—Inserts a new line into the Web page (varchar2). Default NULL. • cwrap—Specifies a wrap style for the document (varchar2). Default NULL. • cattributes—Settings for attributes of HTML tags (varchar2). Default NULL. Listing 7.37 displays a PL/SQL code example using the htp.olistOpen procedure, and Listing 7.38 shows the HTML code generated by this procedure. Listing 7.37 PL/SQL code using htp.olistOpen.<br />
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create or replace procedure olistprc as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.olistOpen Example'); htp.headClose; htp.bodyOpen; htp.olistOpen; htp.listItem('Olist htp.listItem('Olist htp.listItem('Olist htp.listItem('Olist htp.olistClose;<br />
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Item: Item: Item: Item:<br />
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Export the table'); Drop the table'); Create the table/indexes'); Import the data');<br />
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htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.38 HTML code using htp.olistOpen. <HTML> <HEAD> <H1>Oracle WebServer htp.olistOpen Example</H1> </HEAD> <BODY> <OL> <LI>Olist Item: Export the table <LI>Olist Item: Drop the table <LI>Olist Item: Create the table/indexes <LI>Olist Item: Import the data </OL> </BODY> </HTML> Figure 7.20 depicts the Web page using htp.olistOpen<br />
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Figure 7.20 A sample Web page using htp.olistOpen.<br />
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htp.para The htp.para hypertext procedure specifies that the text preceding it. There are no parameters associated with this procedure.<br />
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The htp.paragraph hypertext procedure defines the text preceding its call as being formatted as a paragraph. This procedure is the same as the htp.para procedure except you are able to define specific formatting characteristics. Parameters: calign(in), cnowrap(in), cclear(in), cattributes(in) • calign—Specifies paragraph text alignment (varchar2). Default NULL. • cnowrap—Specifies that text wrapping is not allowed (varchar2). Default NULL. • cclear—Inserts a new line into the Web page (varchar2). Default NULL. • cattributes—Settings for attributes of HTML tags (varchar2). Default NULL.<br />
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htp.plaintext The htp.plaintext hypertext procedure generates a pair of HTML tags that mark the text as being fixed-width. Plain text is one of the most common text formats used within documents. Parameters: ctext(in), cattributes(in) • ctext—Specifies the text to be formatted (varchar2). • cattributes—Settings for attributes of HTML tags (varchar2). Default NULL.<br />
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htp.preClose The htp.preClose hypertext procedure closes a section of text defined as preformatted. Preformatted text appears exactly as it is typed. There are no parameters for this procedure. The preformatted section of text is opened by the procedure htp.preOpen.<br />
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htp.preOpen The htp.preOpen hypertext procedure sets preformatted text on a Web page. Web browsers normally format HTML text and ignore any miscellaneous spaces, tabs, or line returns. Preformatted text would be displayed exactly as it is typed, including the spaces, tabs, and line returns. In the example in Listing 7.39, we see the htp.header information being centered on the Web page. Parameters: cclear(in), cwidth(in), cattributes(in) • cclear—Specifies the insertion of a new line (varchar2). Default NULL. • cwidth—Specifies the fixed-width for the text characters (varchar2). Default NULL. • cattributes—Settings for attributes of HTML tags (varchar2). Default NULL. Listing 7.39 displays a PL/SQL code example using the htp.preOpen procedure, and Listing 7.40 shows the HTML code generated by this procedure. Listing 7.39 PL/SQL code using htp.preOpen.<br />
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create or replace procedure s00 as BEGIN htp.htmlOpen; htp.headOpen; htp.title('s00'); htp.preOpen; htp.header(1,' htp.header(1,' htp.headClose; htp.preClose; htp.formClose; htp.bodyClose; htp.htmlClose; end; / show errors<br />
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Oracle Information Database'); Main Menu','C');<br />
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Listing 7.40 HTML code using htp.preOpen. <HTML> <HEAD> <TITLE>s00</TITLE> <PRE> <H1> Oracle Information Database</H1> <H1 ALIGN="C"> Main Menu</H1> </HEAD> </PRE> </FORM> </BODY> </HTML> Figure 7.21 depicts the Web page using htp.preOpen.<br />
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Figure 7.21 A sample Web page using htp.preOpen.<br />
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htp.p The htp.p hypertext procedure is the alias for the procedure htp.print. The same parameters apply in both cases.<br />
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htp.print The htp.print hypertext procedure displays text on an HTML document. The input data can be typed as either varchar2, date, or number.<br />
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Parameters: ctext(in) • ctext—Specifies the text to be displayed (varchar2, date, or number).<br />
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htp.prints The htp.prints hypertext procedure displays a line of text within a Web page after replacing all occurrences of certain special characters within the text. Without replacing these special characters, they can be confused with HTML control characters and disrupt the whole process. The special characters that are replaced include: • • • •<br />
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& replaced with ‘&’ “ replaced with ‘"’ < replaced with ‘<’ > replaced with ‘>’<br />
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Parameters: ctext(in) • ctext—Specifies the text to be displayed (varchar2, date, or number).<br />
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htp.ps The htp.ps hypertext procedure is the alias for the procedure htp.prints. The parameters are the same for both procedures.<br />
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htp.s The htp.s hypertext procedure generates HTML tags that specify text as being displayed in the format where a line is drawn through the text. This display format may be useful for deemphasizing certain text on a Web page. Parameters: ctext(in), cattributes(in)<br />
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• ctext—Defines the text displayed on the Web document (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.41 displays the PL/SQL code example using the htp.s procedure, and Listing 7.42 shows the HTML code generated by this procedure. Listing 7.41 PL/SQL code using htp.s. create or replace procedure sproc as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.s Example'); htp.headClose; htp.bodyOpen; htp.print('This is a sample of normal text'); htp.nl; htp.s('This is a sample of s text'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.42 HTML code using htp.s. <HTML> <HEAD> <H1>Oracle WebServer htp.s Example</H1> </HEAD> <BODY> This is a sample of normal text <BR> <S>This is a sample of s text</S> </BODY> </HTML> Figure 7.22 depicts the Web page using htp.s.<br />
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Figure 7.22 A sample Web page using htp.s.<br />
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htp.sample The htp.sample hypertext procedure generates a pair of HTML tags that mark a section of text as a sequence of characters. The text is displayed exactly in the sequence it is typed. Parameters: ctext(in), cattributes(in) • ctext—Identifies the text displayed on the document (varchar2). • cattributes—Settings for HTML tag attributes (varchar2). Default NULL.<br />
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Listing 7.43 displays a PL/SQL code example using the htp.sample procedure, and Listing 7.44 shows the HTML code generated by this procedure. Listing 7.43 PL/SQL code using htp.sample. create or replace procedure sample as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.sample Example'); htp.headClose; htp.bodyOpen; htp.sample('This is a test of the htp.sample procedure. Here are some special characters to play with: $ % < & # *'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.44 HTML code using htp.sample. <HTML> <HEAD> <H1>Oracle WebServer htp.sample Example</H1> </HEAD> <BODY> <SAMP>This is a test of the htp.sample procedure. Here are some special characters to play with: $ % < & # *</SAMP> </BODY> </HTML> Figure 7.23 depicts the Web page using htp.sample.<br />
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Figure 7.23 A sample Web page usaing htp.sample.<br />
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htp.small The htp.small hypertext procedure generates HTML tags to mark a section of text with a small font size. Using this procedure can help differentiate sections within a Web page. Parameters: ctext(in), cattributes(in) • ctext—Identifies the text displayed in the document (varchar2). • cattributes—Settings for HTML tag attributes (varchar2). Default NULL. Listing 7.45 displays a PL/SQL code example using the htp.small procedure, and Listing 7.46 shows the HTML code generated by this procedure Listing 7.45 PL/SQL code using htp.small.<br />
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create or replace procedure small as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.small Example'); htp.headClose; htp.bodyOpen; htp.print('This is a sample of text with normal-sized font'); htp.nl; htp.small('This is a sample of text with small-sized font'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.46 HTML code using htp.small. <HTML> <HEAD> <H1>Oracle WebServer htp.small Example</H1> </HEAD> <BODY> This is a sample of text with normal-sized font <BR> <SMALL>This is a sample of text with small-sized font</SMALL> </BODY> </HTML> Figure 7.24 depicts the Web page using htp.small.<br />
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Figure 7.24 A sample Web page using htp.small.<br />
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htp.strike The htp.strike hypertext procedure generates HTML tags that specify text as being displayed in the strikethrough format. This is a good way to highlight text so that it stands out on a Web page. Specifically, notice in Figure 7.25 that the text has a line drawn through it.<br />
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Figure 7.25 A sample Web page using htp.strike. Parameters: ctext(in), cattributes(in) • ctext—Defines the text to be displayed on a Web page (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.47 displays a PL/SQL code example using the htp.strike procedure, and Listing 7.48 shows the HTML code generated by this procedure. Listing 7.47 PL/SQL code using htp.strike. create or replace procedure strike as begin htp.htmlOpen; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/235-239.html (1 of 4)4/03/2005 6:15:52<br />
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htp.headOpen; htp.header(1,'Oracle WebServer htp.strike Example'); htp.headClose; htp.bodyOpen; htp.print('This is a sample of normal text'); htp.nl; htp.strike('This is a sample of strikethrough text'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.48 HTML code using htp.strike. <HTML> <HEAD> <H1>Oracle WebServer htp.strike Example</H1> </HEAD> <BODY> This is a sample of normal text <BR> <STRIKE>This is a sample of strikethrough text</STRIKE> </BODY> </HTML> Figure 7.25 depicts the Web page using htp.strike.<br />
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htp.strong The htp.strong hypertext procedure is functionally identical for most browsers to the htp.bold hypertext procedure. Again, it is a way to emphasize text. Parameters: ctext(in), cattributes(in) • ctext—Defines the text to be displayed on the document (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.49 displays a PL/SQL code example using the htp.strong procedure and Listing 7.50 shows the HTML code generated by this procedure. Listing 7.49 PL/SQL code using htp.strong. create or replace procedure strong as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.strong Example'); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/235-239.html (2 of 4)4/03/2005 6:15:52<br />
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Oracle Databases on the Web:WebServer's HTP Utilities<br />
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htp.headClose; htp.bodyOpen; htp.strong('This is a sample of strong-formatted text'); htp.nl; htp.bold('This is a sample of bold-formatted text'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.50 HTML code using htp.strong. <HTML> <HEAD> <H1>Oracle WebServer htp.strong Example</H1> </HEAD> <BODY> <STRONG>This is a sample of strong-formatted text</STRONG> <BR> <B>This is a sample of bold-formatted text</B> </BODY> </HTML> Figure 7.26 depicts the Web page using htp.strong.<br />
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Figure 7.26 A sample Web page using htp.strong.<br />
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htp.sub The htp.sub hypertext procedure generates HTML tags that mark text as a subscript. Basically, it changes the text to a smaller font size. Parameters: ctext(in), calign(in), cattributes(in) • ctext—Defines the text to be displayed as subscript (varchar2). • calign—Specifies how to align the text (varchar2). Default NULL. • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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htp.sup The htp.sup hypertext procedure displays text as superscript. The font size of the text is smaller than that presented by the procedure htp.sub. Parameters: ctext(in), calign(in), cattributes(in)<br />
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• ctext—Defines the text displayed as superscript (varchar2). • calign—Specifies how to align the text (varchar2). Default NULL. • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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htp.tableCaption The htp.tableCaption hypertext procedure inserts a caption into the inserted table. The caption is not required for a table and can be aligned at the top or bottom. Parameters: ccaption(in), calign(in), cattributes(in) • ccaption—Defines the text of the caption (varchar2). • calign—Specifies how to align the text (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.tableClose The htp.tableClose hypertext procedure closes an HTML table. This tag is generally used when you are done displaying data from a table and you want to continue building your Web page. There are no parameters related to this procedure.<br />
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htp.tableData The htp.tableData hypertext procedure inserts data into an HTML table. HTML table data is organized by cells, which comprise a row. Parameters: cvalue(in), calign(in), cdp(in), crowspan(in), ccolspan(in), cnowrap(in), cattributes(in) • cvalue—Defines the value to be inserted into the HTML table (varchar2). Default NULL. • calign—Specifies how to align the value within the table cell (varchar2). Default NULL. • cdp—Lets the parameter default to null (varchar2). Default NULL. • crowspan—Indicates the number of rows to span in the table (varchar2). Rows can be spanned by grouping cells that apply to several horizontal entries in the table. Default NULL. • ccolspan—Indicates the number of columns to span in the table (varchar2). Span columns when you want to group cells for more than one column in a table. The spanned columns could fall under the same heading. Default NULL. • cnowrap—Specifies that text will not wrap within the cell (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL. Listing 7.51 displays a PL/SQL code example using the htp.tableData procedure, and Listing 7.52 shows the HTML code generated by this procedure. All proprietary information has been replaced with an x. Listing 7.51 PL/SQL code using htp.tableData. create or replace procedure s10b(host_name_in in varchar2) as BEGIN htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's10');<br />
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htp.htmlOpen; htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; htp.nl; htp.nl; for host_rec in ( select rowid, a.host_name, a.ip_address, a.cust_name, a.os_type, a.os_version, a.oracle_csi_nbr, a.dba_pager_nbr from host a where host_name = rtrim(host_name_in)) loop htp.tableData(htf.anchor('update_host?my_rowid='||hostrec.rowid, 'modify this host')); htp.print('Host Name: '); htp.formText('host_name',10,50,host_rec.host_name); htp.print('IP address: '); htp.formText('ip_address',20,50,host_rec.ip_address); htp.print('Customer_name: '); htp.formText('cust_name',10,50,host_rec.cust_name); htp.print('Operating System: '); htp.formText('os_type',10,50,host_rec.os_type); htp.print('Operating System version: '); htp.formText('os_version',10,50,host_rec.os_version); htp.print('Oracle CSI Number: '); htp.formText('oracle_csi_nbr',10,50,host_rec.oracle_csi_nbr); htp.print('DBA pager number: '); htp.formText('dba_pager_nbr',10,50,host_rec.dba_pager_nbr); end loop; htp.nl; htp.nl; htp.nl; htp.formClose; htp.bodyClose; htp.htmlClose; end; /<br />
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show errors Listing 7.52 HTML code using htp.tableData. <BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <HTML> <HEAD> <TITLE>s10</TITLE> <H1>Oracle information database</H1> <H1 ALIGN="C">Host Display</H1> </HEAD> <TD><A HREF="update_host?my_rowid=0000000F.0000.0005" rel="nofollow">Update this host </A></TD> <BR> <BR> Host Name: <INPUT TYPE="text" NAME="host_name" SIZE="10" MAXLENGTH="50" VALUE="xxxxxxx"> IP address: <INPUT TYPE="text" NAME="ip_address" SIZE="20" MAXLENGTH="50" VALUE="xxx.xxx.xxx.xx"> Customer_name: <INPUT TYPE="text" NAME="cust_name" SIZE="10" MAXLENGTH="50" VALUE="XXXXX"> Operating System: <INPUT TYPE="text" NAME="os_type" SIZE="10" MAXLENGTH="50" VALUE="Solaris"> Operating System version: <INPUT TYPE="text" NAME="os_version" SIZE="10" MAXLENGTH="50" VALUE="2.5"> Oracle CSI Number: <INPUT TYPE="text" NAME="oracle_csi_nbr" SIZE="10" MAXLENGTH="50" VALUE="1234567"> DBA pager number: <INPUT TYPE="text" NAME="dba_pager_nbr" SIZE="10" MAXLENGTH="50" VALUE="xxx-xxxx"> <BR> <BR> </FORM> </BODY> </HTML> Figure 7.27 depicts the Web page using htp.tableData.<br />
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Figure 7.27 A sample Web page using htp.tableData.<br />
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htp.tableHeader The htp.tableHeader hypertext procedure creates a table header. There are several parameters that can be passed to determine the characteristics of header text. Parameters: cvalue(in), calign(in), cdp(in), crowspan(in), ccolspan(in), cnowrap(in), cattributes(in) • cvalue—Defines the header text to be inserted into the HTML table (varchar2). Default file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/239-244.html (3 of 4)4/03/2005 6:15:53<br />
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NULL. • calign—Specifies how to align the header text within table cells (varchar2). Default NULL. • cdp—Lets this parameter default to null (varchar2). Default NULL. • crowspan—Indicates the number of rows to span in the table (varchar2). Rows can be spanned by grouping cells that apply to several horizontal entries in the table. Default NULL. • ccolspan—Identifies the number of columns to span in the table (varchar2). Span columns when you want to group cells for more than one column in a table. The spanned columns would fall under the same heading. Default NULL. • cnowrap—Specifies that text will not wrap for the header (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.tableOpen The htp.tableOpen hypertext procedure opens an HTML table. Note that an HTML table is not necessarily the same thing as an Oracle table, but Oracle tables are generally displayed on a Web page using this tag. Parameters: cborder(in), calign(in), cnowrap(in), cclear(in), cattributes(in) • cborder—Indicates whether you want borders around each cell. This is the width of the outside frame measured in pixels (varchar2). Default NULL. • calign—Specifies how to align the table (varchar2). Default NULL. • cnowrap—Specifies that the table is defined without text wrapping (varchar2). Default NULL. • cclear—Inserts a new line into the table (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.tableRowClose The htp.tableRowClose hypertext procedure is used after htp.tableRowOpen has been called to insert a row tag into an HTML table. Procedure htp.tableRowClose should always follow the htp.tableRowOpen call. There are no parameters associated with this procedure.<br />
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htp.tableRowOpen The htp.tableRowOpen hypertext procedure inserts a row tag into an HTML table within a Web page. There are certain alignment issues to be addressed for the table rows. Parameters: calign(in), cvalign(in), cdp(in), cnowrap(in), cattributes(in) • calign—Aligns table rows horizontally (varchar2). Valid values include left, right, and center. Default NULL. • cvalign—Aligns table rows vertically (varchar2). Valid values include top, middle, and bottom. Default NULL. • cdp—Lets this parameter default to null. (varchar2). Default NULL. • cnowrap—Specifies that the table row is defined without text wrapping (varchar2). Default NULL. • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.teletype The htp.teletype hypertext procedure displays text within a Web document as typewriter font. This font is especially useful when displaying program code because the characters are fixed-width. Parameters: ctext(in), cattributes(in) • ctext—Indicates the text displayed on the Web document (varchar2). • cattributes—Attribute settings for HTML tags (varchar2). Default NULL.<br />
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htp.title The htp.title hypertext procedure is used to create a title section for a Web page. As we recall, a title is the name of the page that appears on the Web browser icon when the browser is minimized. Parameters: ctitle(in) • ctitle—Indicates the text displayed for the title on the Web document (varchar2).<br />
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htp.ulistClose The htp.ulistClose hypertext procedure generates an HTML tag to close a list of items that are in no particular order (unordered list). The items will be marked with bullets to help differentiate the items in the list. There are no parameters for this procedure.<br />
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Note: See procedure htp.ulistOpen for examples of the PL/SQL and HTML code related to this procedure.<br />
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htp.ulistOpen The htp.ulistOpen hypertext procedure generates an HTML tag to begin an unordered list of items. The items are differentiated with bullet marks in the first position of each line on the Web page. Parameters: cclear(in), cwrap(in), cparm(in), csrc(in), cattributes(in) • • • • •<br />
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cclear—Inserts a new line into the document (varchar2). Default NULL. cwrap—Specifies a wrap style (varchar2). Default NULL. cparm—Lets this parameter default to NULL. csrc—Identifies an image source (varchar2). Default NULL. cattributes—Settings for HTML tag attributes (varchar2). Default NULL.<br />
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Listing 7.53 displays a PL/SQL code example using the htp.ulistOpen procedure, and Listing 7.54 shows the HTML code generated by this procedure. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch07/244-248.html (2 of 4)4/03/2005 6:15:53<br />
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Listing 7.53 PL/SQL code using htp.ulistOpen. create or replace procedure ulistprc as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer htp.ulistOpen Example'); htp.headClose; htp.bodyOpen; htp.ulistOpen; htp.listItem('Ulist htp.listItem('Ulist htp.listItem('Ulist htp.listItem('Ulist htp.ulistClose;<br />
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Item: Item: Item: Item:<br />
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Export the table'); Drop the table'); Create the table/indexes'); Import the data');<br />
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htp.bodyClose; htp.htmlClose; end; / show errors Listing 7.54 HTML code using htp.ulistOpen. <HTML> <HEAD> <H1>Oracle WebServer htp.ulistOpen Example</H1> </HEAD> <BODY> <UL> <LI>Ulist Item: Export the table <LI>Ulist Item: Drop the table <LI>Ulist Item: Create the table/indexes <LI>Ulist Item: Import the data </UL> </BODY> </HTML> Figure 7.28 depicts the Web page using htp.ulistOpen.<br />
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Figure 7.28 A sample Web page using htp.ulistOpen.<br />
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htp.variable The htp.variable hypertext procedure generates an HTML tag that marks specified<br />
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text as a variable. As we know from our discussions about the CGI, these environment variables are used for passing user input and other information between the browser and Web server. This procedure highlights text (usually italicized) to represent a variable name. It is strictly text presented on the Web page—nothing more. Parameters: ctext(in), cattributes(in) • ctext—Defines the name of the variable (varchar2). • cattributes—Settings for the attributes of HTML tags (varchar2). Default NULL.<br />
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htp.wbr The htp.wbr hypertext procedure is used to generate an HTML tag that will insert a line break into text defined with procedure htp.nobr (for no line breaking). There are no parameters for this hypertext procedure.<br />
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Summary In this chapter we have reviewed the hypertext procedures and functions provided by Oracle WebServer that are built on top of the common HTML tags used to construct Web documents. These functional modules of code simplify the task of tagging HTML documents, making development on the Web a more productive process. Moving on to Chapter 8, we will learn about a full suite of PL/SQL utilities included with Oracle WebServer that are built on the hypertext procedures and functions found in this chapter, and which enhance the functionality of Web documents.<br />
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CHAPTER 8 WebServer’s OWA Utilities The OWA utilities are a set of procedures built on hypertext procedures and functions. These commonly used procedures are designed to save the developer from writing code for basic processes. There are several Oracle packages that contain OWA utilities. The source code for these packages is found in $ORACLE_HOME/ows2/admin: • OWA_COOKIE package—Used to send opaque strings (cookies) to and from a client browser. • OWA_IMAGE package—Used to handle image maps. The functions in this package include: • owa_image.get_x • owa_image.get_y • OWA_INIT package—Used to adjust time zone variations with cookies, which are strings that contain static information about client sessions. There are no procedures or functions within this package, but rather constants that have values assigned. • OWA_PARMS package—Assists in the process of updating database tables and includes: • owa_parms.get • owa_parms.register • OWA_PATTERN package—Contains a set of procedures and functions that allow for the manipulation of strings, including: • owa_pattern.amatch (versions 1 through 4) • owa_pattern.change (versions 1 through 4) • owa_pattern.getpat • owa_pattern.match (versions 1 through 6) • OWA_TEXT package—Contains procedures and functions used to format text, as well as some special data types used in unique situations. These procedures are most often called by the procedures in the OWA_PATTERN package. Included in this package are the following<br />
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procedures and functions: • owa_text.add2multi • owa_text.new_row_list • owa_text.print_multi • owa_text.print_row_list • owa_text.stream2multi • OWA_UTIL package—A helpful set of standard utility procedures, which are integrated with the hypertext procedures and functions and include: • owa_util.get_cgi_env • owa_util.get_owa_service_path • owa_util.http_header_close • owa_util.mime_header • owa_util.print_cgi_env • owa_util.redirect_url • owa_util.showpage • owa_util.showsource • owa_util.signature (versions 1 and 2) • owa_util.status_line • owa_util.tableprint<br />
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Parameter Data Types ProcessedBy OWA Utilities The parameters processed by the procedures and functions that comprise the OWA packages are defined as being one of several data types. These would include the standard data types varchar2, integer, and date, as well as other special types defined specifically for use by Oracle WebServer. OWA Cookie Procedures And Functions A cookie is a file or a data item left on your PC after you have connected to a Web page. In general, a cookie allows WebServer to record information about which screens you have accessed, the name of your internal userid, and other application-specific information. Prior to 1996, cookies were generally sent to the server, but today cookies often reside on client PCs. When accessing an unknown Web page, most savvy Web surfers refuse to allow the page to store a cookie on their PC to avoid introducing a virus. Most cookies are set to expire after a specific date. In any case, cookies are very useful for enabling an Oracle WebServer application to record information about users’ previous visits to a Web page. Cookie files are generally transmitted to the PC on an as-needed basis and are generally read from the PC when the Web page is accessed. The following cookie utilities allow a WebServer developer to control the transmission of cookie files to and from their Oracle server. Chances are, you already have some cookie files on your PC. For example, here is the cookie file for the Netscape Web browser: # Netscape HTTP Cookie File # http://www.netscape.com/newsref/std/cookie_spec.html # This is a generated file! Do not edit. cgi.netscape.com FALSE / FALSE 946688399 NETSCAPE_VERIFY c65ff94b,c6e478a8.infoseek.com TRUE / FALSE 860790378 InfoseekUserId 2D8954B6F8AD5B48EC8BBECAA68A6855 .adobe.com TRUE / FALSE 946688399 INTERSE 111.220.251.2213076838220232573 .focalink.com TRUE / FALSE 946645200 SB_ID ads01.24798843750464250672 For Oracle’s WebServer, a cookie file can be used to remember the session information from each user’s last visit to your Web page. Information, such as user preferences and the values for input file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/249-252.html (2 of 3)4/03/2005 6:15:54<br />
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forms, can be kept in a cookie file. Following is a description of the OWA_COOKIE procedures and functions.<br />
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OWA_COOKIE.GET The owa_cookie.get function accepts a text string and converts it into a cookie file. For example: owa_cookie.get('This will become a cookie file'); Parameters: cname(in) • cname—String used to generate a cookie (varchar2).<br />
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OWA_COOKIE.GET_ALL The owa_cookie.get_all procedure returns all cookie name/value pairs from the client’s browser associated with your WebServer session. This procedure returns an array of the names and values of the cookies as they were processed, and a count of the name/value combinations. Parameters: name(out), value(out), num_values(out) • name—Name of the cookie (owa_text.vc_arr). • value—Values associated with the cookie. A cookie may have multiple values associated with it (owa_text.vc_arr). • num_values—The number of occurrences of name/value pairs for the cookies (integer).<br />
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OWA_COOKIE.REMOVE The owa_cookie.remove procedure is used to expire a cookie, making it immediately noneffective. The output of this procedure must be embedded into an HTML header to enable its successful execution. Parameters: name(in), value(in), path(in) • name—Name of the cookie (varchar2). file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/252-255.html (1 of 4)4/03/2005 6:15:55<br />
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• value—Value associated with the cookie (varchar2). • path—Path of the cookie (varchar2). Default NULL.<br />
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OWA_COOKIE.SEND The owa_cookie.send procedure is used to send a cookie to a client station and must be used with the HTTP header output of the OWA procedure. Parameters: name(in), value(in), expires(in), path(in), domain(in), secure(in) • name—Name of the cookie (owa_text.vc_arr). • value—Value associated with the cookie (owa_text.vc_arr). • expires—Expiration date for the cookie (date). Default NULL. • path—Path of the cookie (varchar2). Default NULL. • domain—Domain for the cookie (varchar2). Default NULL. • secure—Security definition of the cookie transmission (varchar2). Default NULL. OWA Image Package The OWA Image Package assists in the handling of Web images. One of the key aspects of Web image management is the management of image maps. When you use an image map, you need to manage the image’s linked areas, called hotspots. The OWA image functions can assist you in defining the coordinates of the image hotspots. Unfortunately, the two OWA image functions do not work within Oracle WebServer 2. Oracle Support indicates that they may work in Oracle WebServer 3.<br />
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OWA_IMAGE.GET_X The owa_image.get_x function produces the X coordinate of a clicked area on an image map. Parameters: xcoord(in) • xcoord—X coordinate of the hotspot clicked on an image map (owa_image. point).<br />
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OWA_IMAGE.GET_Y The owa_image.get_y function produces the Y coordinate of a clicked area on an image map. Parameters: ycoord(in) • ycoord—Y coordinate of the hotspot clicked on an image map (owa_image. point). OWA Init Package<br />
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The OWA Init Package allows for the changing of constants that define the time zone used by cookies. See the OWA Cookie Procedures And Functions section in this chapter for more information about cookies. Expiration dates used by cookies are defined in Greenwich Mean Time (GMT), and should be reset to the time zone in which your Web page is running. This time zone can be adjusted via one of two constants, depending on your circumstances. If your time zone is recognized by Oracle WebServer (see Table 8.1), then you can set it using the constant dbms_server_timezone. If you are located in an unrecognized time zone, the constant dbms_server_gmtdiff can be used to specify the offset of your time zone from GMT. The script used in this process is located at $ORACLE_HOME/ows2/ admin/pubinit.sql, where the constants can be defined as follows: dbms_server_timezone<br />
<br />
constant varchar2(3) := 'BST'<br />
<br />
Table 8.1Time zones recognized by Oracle WebServer. Abbreviation<br />
<br />
Time Zone<br />
<br />
AST or ADT<br />
<br />
Atlantic Standard or Daylight Time<br />
<br />
BST or BDT<br />
<br />
Bering Standard or Daylight Time<br />
<br />
CST or CDT<br />
<br />
Central Standard or Daylight Time<br />
<br />
EST or EDT<br />
<br />
Eastern Standard or Daylight Time<br />
<br />
GMT<br />
<br />
Greenwich Mean Time<br />
<br />
HST or HDT<br />
<br />
Alaska-Hawaii Standard or Daylight Time<br />
<br />
MST or MDT<br />
<br />
Mountain Standard or Daylight Time<br />
<br />
NST or NDT<br />
<br />
Newfoundland Standard or Daylight Time<br />
<br />
PST or PDT<br />
<br />
Pacific Standard or Daylight Time<br />
<br />
YST or YDT<br />
<br />
Yukon Standard or Daylight Time<br />
<br />
In this example, if you are located in the easternmost part of Siberia, you would set the time zone to string BST. If you need to set the number of hours that your time zone differs from GMT (a positive number is used to set your time ahead of GMT and a negative number for behind GMT), then set the following constant: dbms_server_gmtdiff<br />
<br />
constant number := NULL<br />
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Once the constants have been reset in the pubinit.sql script, then re-create the OWA_INIT package.<br />
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OWA Parms Procedures And Functions The OWA Parms procedures and functions support the updating of database tables from Web pages. Using PL/SQL arrays, which are tables of varchar2(2000) rows, is essential for successfully processing the update requests.<br />
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Note: This package is not included with Oracle WebServer 2.0, but is included with versions 2.1 and higher.<br />
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The script that creates this package is located in $ORACLE_HOME/ ows2/admin/ owa_parms.sql and can be copied from a WebServer 2.1 installation if you want to use it with WebServer 2.0. This package must be created with the userid associated with the OWA_DBA DCD. Also, execute privileges must be granted on the procedures to public, and public synonyms created for those procedures.<br />
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OWA_PARMS.GET The owa_parms.get function retrieves the field names and values from a PL/SQL array. These values can be placed in a record to be used in updating a table row. Parameters: pname(in) returns varchar2<br />
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• pname—Name of the field whose value will be retrieved from the PL/SQL array (owa_parms.array).<br />
<br />
OWA_PARMS.REGISTER The owa_parms.register procedure loads a PL/SQL array with field names and values. These names and values can be used for subsequent processing and are indexed by binary integers. Parameters: pname(in), pvalue(in) • pname—Name of the field (owa_parms.array). • pvalue—Value of the field (owa_parms.array).<br />
<br />
OWA_PARMS_DEMO_FORM The owa_parms_demo_form procedure is not a part of the OWA Parms package but is included in the owa_parms.sql script as an example. The procedure submits a form that shows how PL/SQL arrays are passed as associative arrays. The field name is analyzed and the values related to this field name are processed in an iterative routine. OWA Pattern Procedures And Functions The OWA Pattern utilities manipulate data strings and include three different types of operations: match, amatch, and change. The match procedures search a string for either a string or pattern and return a boolean TRUE or FALSE. The amatch procedures allow the user to specify where in a target string to search for a string or pattern, and return the location where the search found a match. To replace the text found in a string and return the number of substitutions made, the change procedures should be used. For each of the manipulation procedures, there are wildcard characters that can provide more options in defining the search strings. (See Table 8.2.) Table 8.2Wildcard characters used for defining search string options. Wildcard<br />
<br />
Meaning<br />
<br />
\n<br />
<br />
Matches newline.<br />
<br />
$<br />
<br />
Matches newline or the end of the target.<br />
<br />
^<br />
<br />
Matches newline or the beginning of the target.<br />
<br />
.(period)<br />
<br />
Matches any character except newline.<br />
<br />
\t<br />
<br />
Matches tab.<br />
<br />
\d<br />
<br />
Matches digits (0 through 9).<br />
<br />
\D<br />
<br />
Matches non-digits (other than 0 through 9).<br />
<br />
\s<br />
<br />
Matches blank, tab, or newline.<br />
<br />
\S<br />
<br />
Matches everything other than blank, tab, or newline.<br />
<br />
\w<br />
<br />
Matches alphanumeric characters.<br />
<br />
\W<br />
<br />
Matches non-alphanumeric characters.<br />
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\b<br />
<br />
Matches boundaries between \w and \W.<br />
<br />
&<br />
<br />
Causes the target string that matched the search string to be included in the string that replaces it. This wildcard only applies to the change procedures.<br />
<br />
Table 8.3 displays extensions that apply to the wildcards (except &) and text that furthers search capabilities. Table 8.3Search string extensions. Extension<br />
<br />
Meaning<br />
<br />
*<br />
<br />
Zero or more occurrences.<br />
<br />
?<br />
<br />
Zero or 1 occurrence.<br />
<br />
+<br />
<br />
1 or more occurrences.<br />
<br />
{n}<br />
<br />
n occurrences.<br />
<br />
{n,}<br />
<br />
A minimum of n occurrences.<br />
<br />
{n,m}<br />
<br />
A minimum of n occurrences, but no more than m.<br />
<br />
In the following example of how to use search string wildcards and extensions, we are searching for the string urf in target string Surfing the Web. owa_pattern.match ('Surfing the Web','urf.+','i'); The period (.) specifies to match any character except newline, and the plus sign (+) instructs to include only 1 or more occurrences of the match.<br />
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OWA_PATTERN.AMATCH (VERSION 1) The owa_pattern.amatch (version 1) function searches a string for a string beginning at a starting position in the target string. A value is returned from the function which is the location of the match. Otherwise, a zero is returned when no match is found. In Listing 8.1, a string is searched for the string gin beginning 12 positions from the start of the target string. The flags parameter is set to i, making the search case-insensitive. Because the search is successful, the message String Found is displayed to the Web page. Parameters: line(in), from_loc(in), string(in), flags(in) • line—String to be searched (varchar2). • from_loc—Number of positions from the start of the target string to begin the search (integer). • string—String to search for in the target string (varchar2). • flags—Settings for interpreting the search (varchar2). Default is NULL. Listing 8.1 shows an example of the owa_pattern.amatch (version 1) procedure. Listing 8.1 The owa_pattern.amatch (version 1) procedure. create or replace procedure amatch1 as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.amatch Example');<br />
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htp.headClose; htp.bodyOpen; htp.print('Search a string from a starting point'); htp.nl; If owa_pattern.amatch('Digital Imaging',12,'gin','i') = 0 then htp.print('String Not Found'); else htp.print('String Found'); end if; htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.2 shows the HTML code generated from the procedure shown in Listing 8.1. Listing 8.2 HTML source code generated from the owa_pattern.amatch (version 1) procedure. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.amatch Example</H1> </HEAD> <BODY> Search a string from a starting point <BR> String Found </BODY> </HTML> The Web page created from this code is depicted in Figure 8.1.<br />
<br />
Figure 8.1 The Web page example for owa_pattern.amatch (version 1).<br />
<br />
OWA_PATTERN.AMATCH (VERSION 2) The owa_pattern.amatch (version 2) function searches a string for a pattern beginning at a starting position in the string being searched. The location of the match is returned as the number of positions from the beginning of the search string. The value zero is returned when no match is found for the pattern. Parameters: line(in), from_loc(in), pat(in,out), flags(in) • line—String to be searched (varchar2). • from_loc—Number of positions from the start of the target string to begin the search (integer). • pat—Pattern to be searched for in the target string (owa_pattern.pattern). • flags—Settings for interpreting the search (varchar2). Default is NULL.<br />
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OWA_PATTERN.AMATCH (VERSION 3) The owa_pattern.amatch (version 3) function searches a target string for a matching string beginning at a starting position in the target string. The location of the match is returned as the number of positions from the beginning of the search string. When no match is found for the pattern, a zero is returned. The optional parameter backrefs is used by this variation of the function and is a PL/SQL table that holds each string in the target that matched the search criteria. Parameters: line(in), from_loc(in), string(in), backrefs(out), flags(in) • line—String to be searched (varchar2). • from_loc—Number of positions from the start of the target string to begin the search (integer). • string—String to be searched for in the target string (varchar2). • backrefs—PL/SQL tables containing the resulting strings that are matched (owa_text.vc_arr). • flags—Settings for interpreting the search, such as the string i for a case-insensitive search (varchar2). Default is NULL.<br />
<br />
OWA_PATTERN.AMATCH (VERSION 4) The owa_pattern.amatch (version 4) function searches a target string for a pattern beginning at a starting position in the target string. The location of the match returns an integer representing the number of positions from the beginning of the search string. A zero is returned when no match is encountered. The optional parameter backrefs is also used by this variation of the function and, as you know, is a PL/SQL table that holds each string in the target that matched the search. Parameters: line(in), from_loc(in), pat(in,out), backrefs(out), flags(in) • line—Target string that will be searched (varchar2). • from_loc—Number of positions from the start of the target string to begin the search (integer). • pat—Pattern to be searched for in the target string (owa_pattern.pattern). • backrefs—PL/SQL tables containing the strings that match the pattern (owa_text. vc_arr). • flags—Settings for interpreting the search (varchar2). Default is NULL.<br />
<br />
OWA_PATTERN.CHANGE (VERSION 1) The owa_pattern.change (version 1) function searches a target string for a string and replaces it. The change functions and procedures can only search for strings and not patterns. The output from this function is the number of revisions that resulted from the search.<br />
<br />
Note: Setting the flags parameter to g only applies to the owa_pattern.change procedure or function and disperses the operation globally, causing all matching occurrences of the search string to be replaced.<br />
<br />
Parameters: line(in,out), from_str(in), to_str(in), flags(in)<br />
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• • • •<br />
<br />
line—String to be searched and revised (varchar2). from_str—String being searched for and, if found, replaced (varchar2). to_str—String that will replace the from string in the target string (varchar2). flags—Settings for interpreting the search (varchar2). Default is NULL.<br />
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OWA_PATTERN.CHANGE (VERSION 2) The owa_pattern.change (version 2) procedure searches a string for a string and replaces it. In Listing 8.3, a string is searched for the string Sabres and is replaced with the string Bills. The flags parameter is set to g, making a global replacement for all occurrences of the search pattern. However, there is only one occurrence for this test. The search and replacement is successful, which is validated by the before and after images of the target string displayed on the Web page. Parameters: line(in,out), from_str(in), to_str(in), flags(in) • line—String to be searched and revised (varchar2). • from_str—String being searched for and, if found, replaced in the target string (varchar2). • to_str—String that will replace the from string in the target string (varchar2). • flags—Interpretive settings for the search (varchar2). Default is NULL. Listing 8.3 shows an example of the owa_pattern.change (version 2) procedure. Listing 8.3 The owa_pattern.change (version 2) procedure. create or replace procedure change2 as charstring varchar2(15); begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.change Example'); htp.headClose; htp.bodyOpen; htp.print('Search a string for a string and replace it'); htp.nl;<br />
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charstring := 'Buffalo Sabres'; htp.print('Before Image: '); htp.print(charstring); owa_pattern.change(charstring,'Sabres','Bills','g'); htp.nl; htp.print('After Image: '); htp.print(charstring); htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.4 shows the HTML code generated from the procedure shown in Listing 8.3. Listing 8.4 HTML source code created from the owa_pattern.change (version 2) procedure. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.change Example</H1> </HEAD> <BODY> Search a string for a string and replace it <BR> Before Image: Buffalo Sabres <BR> After Image: Buffalo Bills </BODY> </HTML> The Web page created from this code is depicted in Figure 8.2.<br />
<br />
Figure 8.2 The Web page example for owa_pattern.change (version 2).<br />
<br />
OWA_PATTERN.CHANGE (VERSION 3) The owa_pattern.change (version 3) function searches a multiple-line string for a string and replaces it. The number of revisions that occur within the multi_line is an output of this function. Parameters: mline(in,out), from_str(in), to_str(in), flags(in) • • • •<br />
<br />
mline—String to be searched and revised (owa_text.multi_line). from_str—String being searched for and, if found, replaced in the target (varchar2). to_str—String that will replace the from string in the target multi_line (varchar2). flags—Settings for processing the search (varchar2). Default is NULL.<br />
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OWA_PATTERN.CHANGE (VERSION 4) The owa_pattern.change (version 4) procedure searches a multiple-line string for a string and replaces it. In Listing 8.5, a multiple-line string is searched for the string Amerks and is to be replaced with the string Americans. Notice in the code that the mline variable is declared with the data type owa_text.multi_line, which is standard for a multi_line variable. The search is successful and replaces the found text as indicated on the Web page with the before and after images. Parameters: mline(in,out), from_str(in), to_str(in), flags(in) • mline—multi_line to be searched and revised (owa_text.multi_line). • from_str—String to be searched for and replaced in the multi_line (varchar2). • to_str—String that will replace the matching from strings found in the multi_line (varchar2). • flags—Settings for interpreting the search (varchar2). Default is NULL. Listing 8.5 shows an example of the owa_pattern.change (version 4) procedure. Listing 8.5 The owa_pattern.change (version 4) procedure. create or replace procedure change4 as charstring varchar2(45); mline owa_text.multi_line; begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.change Example'); htp.headClose; htp.bodyOpen; htp.print('Search a multi_line for a string and replace it'); htp.nl; charstring := 'The Rochester Amerks are Calder Cup Champions'; htp.print('Before Image: '); htp.print(charstring); owa_text.stream2multi(charstring,mline); owa_pattern.change(mline,'Amerks','Americans','g'); htp.nl; htp.print('After Image: '); owa_text.print_multi(mline); htp.bodyClose; htp.htmlClose; end; /<br />
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show errors Listing 8.6 shows the HTML code generated from this procedure. Listing 8.6 HTML source code for the procedure shown in Listing 8.5. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.change Example</H1> </HEAD> <BODY> Search a multi_line for a string and replace it <BR> Before Image: The Rochester Amerks are Calder Cup Champions <BR> After Image: The Rochester Americans are Calder Cup Champions </BODY> </HTML> The Web page created from this code is depicted in Figure 8.3.<br />
<br />
Figure 8.3 The Web page example for owa_pattern.change (version 2).<br />
<br />
OWA_PATTERN.GETPAT The owa_pattern.getpat procedure converts a string defined as varchar2 to the special data type owa_pattern.pattern for use in pattern searching operations via the OWA Pattern package. Parameters: arg(in), pat(in,out) • arg—String to be converted to the special data type (varchar2). • pat—Pattern generated by the conversion of the input string (owa_pattern.pattern). Refer to the owa_pattern.match (version 4) section in this chapter for an example of the owa_pattern.getpat procedure.<br />
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OWA_PATTERN.MATCH (VERSION 1) The owa_pattern.match (version 1) function searches a target string for a string and returns a boolean TRUE or FALSE. In Listing 8.7, a string is searched for the string hal. The flags parameter is set to i, which makes the search case-insensitive. Because the search is successful, the message The Search has found a Match is displayed to the Web page, as shown in Figure 8.4.<br />
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Figure 8.4 The Web page example for owa_pattern.match (version 1). Parameters: line(in), string(in), flags(in) • line—Target string to be searched (varchar2). • string—String to search for in the target string (varchar2). • flags—Interpretive settings for the search (varchar2). Default is NULL. Listing 8.7 shows an example of the owa_pattern.match (version 1) function. Listing 8.7 The owa_pattern.match (version 1) function. create or replace procedure match1 as begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.match Example'); htp.headClose; htp.bodyOpen; htp.print('Search a string for a string'); htp.nl; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/266-270.html (1 of 4)4/03/2005 6:15:57<br />
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If owa_pattern.match('Silver Halide','hal','i') = TRUE then htp.print('The Search has found a Match'); end if; htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.8 displays the HTML code generated from the function shown in Listing 8.7. Listing 8.8 HTML source code for the function shown in Listing 8.7. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.match Example</H1> </HEAD> <BODY> Search a string for a string <BR> The Search has found a Match </BODY> </HTML> The Web page created from this code is depicted in Figure 8.4.<br />
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OWA_PATTERN.MATCH (VERSION 2) The owa_pattern.match (version 2) function searches a target string for a pattern. A boolean TRUE or FALSE will be returned from the function.<br />
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Note: A pattern is a PL/SQL table of 4-byte varchar2 strings that provides another way of storing a regular string defined with the varchar2 data type. One of the reasons for wanting to use a pattern for searching instead of a regular string is that the pattern can be an input or output parameter. Using the pattern as an output would eliminate multiple parsing of the pattern when the same pattern is passed to other owa_pattern calls.<br />
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Parameters: line(in), pat(in,out), flags(in) • line—String to be searched (varchar2). • pat—Pattern to search for in the target string (owa_pattern.pattern). • flags—Settings for processing the search (varchar2). Default is NULL.<br />
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OWA_PATTERN.MATCH (VERSION 3) The owa_pattern.match (version 3) function searches a target string for a string and returns a boolean TRUE or FALSE. This function also uses the parameter backrefs, which is a PL/SQL table of strings that match the target string. Parameters: line(in), string(in), backrefs(out), flags(in) • line—Target string to be searched (varchar2). • string—String to search for in the target string (varchar2). file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/266-270.html (2 of 4)4/03/2005 6:15:57<br />
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• backrefs—An output parameter that is a PL/SQL table that holds each string matched in the target (owa_text.vc_arr). • flags—Settings for interpreting the search criteria (varchar2). Default is NULL.<br />
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OWA_PATTERN.MATCH (VERSION 4) The owa_pattern.match (version 4) function searches a target string for a pattern and returns a boolean TRUE or FALSE. In Listing 8.9, a string is searched for the FAL. pattern. Notice that a period was placed just after the three characters FAL, which is a wildcard token that will match any character except newline. The search is successful because the flags parameter was set to allow for a caseinsensitive search. The message The Search has found a Matching Pattern is posted to the Web page to validate the test. (See Figure 8.5.)<br />
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Figure 8.5 The Web page example for owa_pattern.match (version 4). Parameters: line(in), pat(in,out), backrefs(out), flags(in) • line—String to be searched (varchar2). • pat—Pattern to search for in the target string (owa_pattern.pattern). • backrefs—An optional output parameter that is a PL/SQL table that holds each string matched in the target (owa_text.vc_arr). • flags—Interpretive settings for the search (varchar2). Default is NULL.<br />
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Note: There are two special data types used in this example for the parameters pat(owa_pattern. pattern) and backrefs (owa_text.vc_arr).<br />
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Listing 8.9 shows an example of the owa_pattern.match (version 4) function. Listing 8.9 The owa_pattern.match (version 4) function. create or replace procedure match4 as patstring owa_pattern.pattern; backrefs owa_text.vc_arr; begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.match Example'); htp.headClose; htp.bodyOpen; htp.print('Search a string for a pattern'); htp.nl; owa_pattern.getpat('FAL.',patstring); If owa_pattern.match('Niagara Falls',patstring,backrefs,'i') = TRUE then htp.print('The Search has found a Matching Pattern'); end if; htp.bodyClose; htp.htmlClose; end; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/266-270.html (3 of 4)4/03/2005 6:15:57<br />
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/ show errors Listing 8.10 shows the HTML source code generated from the owa_pattern.match (version 4) procedure shown in Listing 8.9. Listing 8.10 The HTML source code for the function shown in Listing 8.9. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.match Example</H1> </HEAD> <BODY> Search a string for a pattern <BR> The Search has found a Matching Pattern </BODY> </HTML> The Web page created from this code is depicted in Figure 8.5.<br />
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OWA_PATTERN.MATCH (VERSION 5) This function searches a target multi_line (multiple-line string) for a string and will return a boolean TRUE or FALSE from the process. In Listing 8.11, the search is successful, finding the string base in lines one and three of the multiple-line string. The Web page displays messages validating the success of the search, as shown in Figure 8.6.<br />
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Figure 8.6 The Web page example for owa_pattern.match (version 5).<br />
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Note: Additional lines were added to the multi_line using the owa_text.add2multi procedure and the row list (parameter rlist) was printed using the procedure owa_text.print_row_list.<br />
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Parameters: mline(in), string(in), rlist(out), flags(in) • mline—Multiple-line string to be searched (owa_text.multi_line). • string—String to search for in the target multi_line (varchar2). • rlist—List of the line numbers in the multi_line where string matches were found from the search (owa_text.row_list). • flags—Settings for interpreting the search (varchar2). Default is NULL.<br />
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Note: There are two special data types used in this example for the parameters mline (owa_text.multi_line) and rlist(owa_text.row_list).<br />
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Listing 8.11 shows an example of the owa_pattern.match (version 5) function.<br />
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Listing 8.11 The owa_pattern.match (version 5) function. create or replace procedure match5 as charstring1 varchar2(50); charstring2 varchar2(50); charstring3 varchar2(50); searchstr varchar2(5); mline owa_text.multi_line; rlist owa_text.row_list; begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_pattern.match Example'); htp.headClose; htp.bodyOpen; htp.print('Search a multi_line for a string'); htp.nl; charstring1 charstring2 charstring3 searchstr<br />
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:= := := :=<br />
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'Database Administrators do it in the Dictionary.'; 'But they have also been known to model a bit.'; 'They have a very strong technology base.'; 'base';<br />
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owa_text.stream2multi(charstring1,mline); owa_text.add2multi(charstring2,mline,FALSE); owa_text.add2multi(charstring3,mline,FALSE); If owa_pattern.match(mline,searchstr,rlist) = TRUE then htp.print('The Search has found a Matching String'); end if; htp.nl; htp.print('Print the line numbers which had a match in the multi_line: '); htp.nl; owa_text.print_row_list(rlist); htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.12 shows the HTML code generated from the owa_pattern.match (version 5) procedure shown in Listing 8.11. Listing 8.12 The HTML source code for the function shown in Listing 8.11. <HTML> <HEAD> <H1>Oracle WebServer owa_pattern.match Example</H1> </HEAD> <BODY><br />
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Search a multi_line for a string <BR> The Search has found a Matching String <BR> Print the line numbers which had a match in the multi_line: <BR> 1 3 </BODY> </HTML> The Web page created from this code is depicted in Figure 8.6.<br />
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OWA_PATTERN.MATCH (VERSION 6) The owa_pattern.match (version 6) function searches a target multi_line for a pattern, and a boolean TRUE or FALSE will be returned. The line numbers in the multi_line that contain the matching pattern will be stored in the row list using parameter rlist. Parameters: mline(in), pat(in,out), rlist(out), flags(in) • mline—Multiple-line string to be searched (owa_text.multi_line). • pat—Pattern to search for in the target multi_line (owa_pattern.pattern). • rlist—List of the line numbers in the multi_line where string matches were found from the search (owa_text.row_list). • flags—Settings for processing the search (varchar2). Default is NULL.<br />
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OWA Text Procedures And Functions The OWA Text class of utilities is used primarily in conjunction with the OWA Pattern procedures and functions, providing functionality for manipulating multiple lines of text and processing special data types.<br />
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OWA_TEXT.ADD2MULTI The owa_text.add2multi procedure allows for content to be added to a multi_line. In Listing 8.13, the continue parameter is set to FALSE, which adds the new content to the multi_line as three new lines rather than appending to the first line. Parameters: stream(in), mline(out), continue(in) • stream—Content string to be added to the multi_line (varchar2). • mline—multi_line to add the content to (owa_text.multi_line). • continue—Determines whether to append to the last line in the multi_line or to start a new line (boolean). Default is TRUE. Listing 8.13 shows an example of the owa_text.add2multi procedure. Listing 8.13 Theowa_text.add2multi procedure. create or replace procedure add2multi as charstring1 varchar2(47); charstring2 varchar2(47); charstring3 varchar2(47); charstring4 varchar2(47); mline owa_text.multi_line; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/273-277.html (1 of 4)4/03/2005 6:15:59<br />
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begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer owa_text.add2multi Example'); htp.headClose; htp.bodyOpen; htp.print('Add content to a multi_line'); htp.nl; charstring1 charstring2 charstring3 charstring4<br />
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:= := := :=<br />
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'This is a test of the Emergency Dating System.'; 'If this had been a real emergency, you would '; 'have been instructed where to tune in for more '; 'information about your next date.';<br />
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owa_text.stream2multi(charstring1,mline); htp.print('Before Image of multi_line: '); owa_text.print_multi(mline); htp.nl; owa_text.add2multi(charstring2,mline,FALSE); owa_text.add2multi(charstring3,mline,FALSE); owa_text.add2multi(charstring4,mline,FALSE); htp.nl; htp.print('After Image of multi_line: '); owa_text.print_multi(mline); htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.14 shows the HTML code generated from the owa_text.add2multi procedure. Listing 8.14 The HTML source code for the procedure shown in Listing 8.13. <HTML> <HEAD> <H1>Oracle WebServer owa_text.add2multi Example</H1> </HEAD> <BODY> Add content to a multi_line <BR> Before Image of multi_line: This is a test of the Emergency Dating System. <BR> <BR> After Image of multi_line: This is a test of the Emergency Dating System. If this had been a real emergency, you would have been instructed where to tune in for more information about your next date. </BODY> </HTML> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/273-277.html (2 of 4)4/03/2005 6:15:59<br />
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The Web page created from this code is depicted in Figure 8.7.<br />
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Figure 8.7 The Web page example for owa_text.add2multi.<br />
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OWA_TEXT.NEW_ROW_LIST The owa_text.new_row_list operation can be a procedure or a function. As a function, it has no input parameters and outputs a new, empty row_list. As a procedure, it inserts into the row_list parameter a new, empty row_list. As you know, row_list contains the line numbers within a multi_line where matches were found from a search. Parameters: rlist(out) • rlist—Parameter normally used to contain a list of line numbers in the multi_line where string matches were found from a search (owa_text.row_list).<br />
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OWA_TEXT.PRINT_MULTI The owa_text.print_multi procedure uses the htp.print procedure behind the scenes to print the strings in a multi_line. A multi_line is a multiple-line string defined with data type owa_text. multi_line. Parameters: mline(in) • mline—multi-line to be printed (owa_text.multi_line).<br />
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Note: To see an example of the owa_text.print_multi, refer to the owa_pattern.change (version 4) section in this chapter.<br />
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OWA_TEXT.PRINT_ROW_LIST The owa_text.print_row_list procedure uses the htp.print procedure to print a list of the line numbers in a multi_line where matches were found from a search. In the example, the special data type owa_text.row_list is used to define the rlist parameter. Parameters: rlist(in) • rlist—List of line numbers resulting from a search of a multi_line (owa_text.row_list).<br />
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Note: To see an example of the owa_text.print_row_list procedure, refer to the owa_pattern. match (version 5) section in this chapter.<br />
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OWA_TEXT.STREAM2MULTI The owa_text.stream2multi procedure converts very long strings (>= 32 K) to the multi_line data type. Parameters: stream(in), mline(out)<br />
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• stream—String to be converted (varchar2). • mline—Multiple-line string that results from the stream (owa_text.multi_line).<br />
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Note: To see an example of the owa_text.stream2multi procedure, refer to the owa_pattern. change (version 4) section in this chapter.<br />
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OWA Util Procedures The OWA Util package of procedures utilizes the hypertext functions and hypertext procedures (htf and htp, respectively) bundled with Oracle WebServer. They can be used to enhance the development of HTML to perform numerous tasks, such as formatting documents, forms, and image maps.<br />
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OWA_UTIL.GET_CGI_ENV The owa_util.get_cgi_env function returns the value of a CGI environment variable. An example of such a variable is path_translated. If the value of the variable is not defined, then a NULL value is returned. Parameters: cname(in) • cname—Name of the CGI environment variable (varchar2). The parameter is case-insensitive.<br />
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OWA_UTIL.GET_OWA_SERVICE_PATH The owa_util.get_owa_service_path function returns the name of the currently active path, which includes the virtual path, the DCD (Database Connection Descriptor), and the PL/SQL Agent executable. The format for the active path returned is /ows-bin/DCD_name/owa/. The currently active path will not include the DCD_name when it defaults to the name of the owa_default_service, which is the user PL/SQL Agent access service. There are no parameters for this function. An example of the use of this utility can be found in the example for owa_util.showsource, where a form is opened by concatenating the active path to the form name.<br />
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OWA_UTIL.HTTP_HEADER_CLOSE The owa_util.http_header_close procedure generates a newline to close an HTTP header, which is a requirement for printing (with htp.print, for example). In some instances, you may not have already closed the HTTP header by specifying bclose_header. There are no parameters for this procedure.<br />
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OWA_UTIL.MIME_HEADER file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/277-281.html (1 of 3)4/03/2005 6:15:59<br />
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The owa_util.mime_header procedure changes the default MIME header returned by the PL/SQL Agent. Remember that MIME identifies the type of document returned to the browser. The parameter mime_header must precede all htp.print and htp.prn calls to allow the default MIME to be changed. Setting the parameter bclose_hdr to TRUE will send two newlines and close the HTTP header. Otherwise, setting it to FALSE will not close the HTTP header because only one newline is sent. Parameters: mime_type(in), bclose_hdr(in) • mime_type—Default MIME type that identifies the content of the files (varchar2). • bclose_hdr—Setting to determine if the HTTP header should be closed or not (boolean). Default is TRUE.<br />
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OWA_UTIL.PRINT_CGI_ENV The owa_util.print_cgi_env procedure prints the values of all the CGI environment variables that are processed between the PL/SQL Agent and the PL/SQL procedures. Remember, the CGI environment variables are used for communication purposes regardless of whether CGI or WRB is used to process the requests. Printing these variables can be tremendously helpful in testing the functionality of your Web pages. For instance, the variables in Listing 8.15 indicate a Gateway_Interface using CGI/1.1 and a Script_Name of /ows-bin/owa (which is the currently active path). A few variables in the following examples have been intentionally blanked-out to protect proprietary information. There are no parameters for this procedure. Listing 8.15 shows an example of the owa_util.print_cgi_env procedure. Listing 8.15 The owa_util.print_cgi_env procedure. create or replace procedure printcgienv as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver owa_util.print_cgi_env'); htp.header(1,'Oracle WebServer owa_util.print_cgi_env Example'); htp.headClose; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 'printcgiform'); htp.print('ENTER Hostname: '); htp.FormText('Hostname',10,50); htp.nl; htp.FormClose; owa_util.print_cgi_env; htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.16 shows the HTML code generated from the owa_util.print_ cgi_env procedure. Listing 8.16 The HTML source code for the procedure shown in Listing 8.15. <HTML> <HEAD> <TITLE>Oracle Webserver owa_util.print_cgi_env</TITLE> <H1>Oracle WebServer owa_util.print_cgi_env Example</H1> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/277-281.html (2 of 3)4/03/2005 6:15:59<br />
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</HEAD> <BODY> <FORM ACTION="/ows-bin/owa/printcgiform" METHOD="POST"> ENTER Hostname: <INPUT TYPE="text" NAME="Hostname" SIZE="10" MAXLENGTH="50"> <BR> </FORM> SERVER_SOFTWARE = Oracle_Web_listener2.0/1.20in2<BR> SERVER_NAME = xxxxxxx<BR> GATEWAY_INTERFACE = CGI/1.1<BR> REMOTE_HOST = <BR> REMOTE_ADDR = xxx.xxx.xx.xx<BR> AUTH_TYPE = <BR> REMOTE_USER = <BR> REMOTE_IDENT = <BR> HTTP_ACCEPT = image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*<BR> HTTP_USER_AGENT = Mozilla/3.0 (Win16; I)<BR> SERVER_PROTOCOL = HTTP/1.0<BR> SERVER_PORT = 8111<BR> SCRIPT_NAME = /ows-bin/owa<BR> PATH_INFO = /printcgienv<BR> PATH_TRANSLATED = /u01/dba/oracle/app/oracle/product/7.3.2/ows2/doc/ printcgienv<BR> HTTP_REFERER = <BR> </BODY> </HTML> The Web page created from this code is depicted in Figure 8.8.<br />
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Figure 8.8 The Web page example for owa_util.print_cgi_env.<br />
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OWA_UTIL.REDIRECT_URL The owa_util.redirect_url procedure redirects the processing of a URL. As in previous examples, the URL may represent a Web page or a program to be executed. This procedure call must precede all htp.print and htp.prn calls to allow the redirect by the PL/SQL Agent to process successfully. The parameter bclose_hdr is defined with the boolean data type. If it is set to TRUE, bclose_hdr will send two newlines and close the HTTP header. If it is set to FALSE, the HTTP header stays open because only one newline is sent. Parameters: curl(in), bclose_hdr(in) • curl—URL to be transferred to (varchar2). • bclose_hdr—Determines whether the HTTP header will be closed or not (boolean). Default is TRUE.<br />
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OWA_UTIL.SHOWPAGE The owa_util.showpage procedure generates the HTML source code for a static Web page (forms won’t be generated) from the output of a PL/SQL procedure and can be accessed in the future as a standard HTML document. This procedure can be executed from SQL *Plus, SQL*DBA, or ServerManager and must use an htp procedure and/or htf function to generate HTML source code. The HTML code is generated into the spool file specified as part of the process. There are no parameters for this procedure. An example of generating the HTML for procedure static through SQL*Plus is shown in Listing 8.17. Listing 8.17 Generating HTML for a PL/SQL procedure via SQL*Plus SQL> set serveroutput on SQL> spool static.html SQL> execute static PL/SQL procedure successfully completed. SQL> execute owa_util.showpage <HTML> <HEAD> <TITLE>Oracle Webserver showpage</TITLE> <H1>Oracle WebServer owa_util.showpage Example</H1> </HEAD> <BODY> This is a test of the Emergency Dating System. If this had been a real emergency, you would have been instructed where to tune in for information about your next date. <BR> </BODY> </HTML> PL/SQL procedure successfully completed.<br />
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OWA_UTIL.SHOWSOURCE The owa_util.showsource utility procedure prints the source code of a PL/SQL package, procedure, or function. This can be very helpful when you want an easy way to display your code while developing your applications. Parameters: cname(in) • cname—Name of the package, procedure, or function whose source code will be displayed (varchar2). Listing 8.18 shows an example of the owa_util.showsource procedure. Listing 8.18 The owa_util.showsource procedure. create or replace procedure showsrc as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver showsrc'); htp.header(1,'Oracle WebServer owa_util.showsource(cname) Example'); htp.headClose; htp.bodyOpen; owa_util.showsource('formimage'); htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.19 shows the HTML code generated from the owa_util.showsource procedure. Listing 8.19 The HTML source code generated from the owa_util.showsource procedure. <HTML> <HEAD> <TITLE>Oracle Webserver showsrc</TITLE> <H1>Oracle WebServer owa_util.showsource(cname) Example</H1> </HEAD> <BODY> <H1>Source code for FORMIMAGE</H1> <PRE> procedure formimage as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver formImage'); htp.header(1,'Oracle WebServer htp.formImage Examples'); htp.headClose; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's00'); htp.print('Click on the Image to submit Form'); htp.FormImage('BobPic','/ows-img/papaj.gif'); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/281-286.html (2 of 5)4/03/2005 6:16:00<br />
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htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; </PRE> <HR> This page was produced by the <B>Oracle Web Agent</B> on October 14, 1996 03:42 PM<BR> </BODY> </HTML> The Web page created from this code is depicted in Figure 8.9.<br />
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Figure 8.9 The Web page example for owa_util.showsource.<br />
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OWA_UTIL.SIGNATURE (VERSION 1) The owa_util.signature (version 1) utility procedure creates a signature line at the bottom of the document to timestamp the page. This feature will assist you in determining when a page was created. There are no parameters for this procedure. Listing 8.20 shows an example of the owa_util.signature (version 1). Listing 8.20 The owa_util.signature (version 1) utility procedure. create or replace procedure signa0 as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver owa_util.signature'); htp.header(1,'Oracle WebServer owa_util.signature Example'); htp.headClose; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 'sigform'); htp.print('Click on the Image to submit Form'); htp.FormImage('flamingo','/ows-img/flamingo.gif'); htp.nl; htp.FormClose; owa_util.signature; htp.bodyClose; htp.htmlClose; end; / show errors Listing 8.21 shows the HTML code generated from the owa_util.signature (version 1) utility procedure.<br />
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Listing 8.21 The HTML source code generated from the procedure shown in Listing 8.20. <HTML> <HEAD> <TITLE>Oracle Webserver owa_util.signature</TITLE> <H1>Oracle WebServer owa_util.signature Example</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/sigform" METHOD="POST"> Click on the Image to submit Form <INPUT TYPE="image" NAME="flamingo" SRC="/ows-img/flamingo.gif"> <BR> </FORM> <HR> This page was produced by the <B>Oracle Web Agent</B> on October 15, 1996 08:37 AM<BR> </BODY> </HTML> The Web page created from this code is depicted in Figure 8.10.<br />
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Figure 8.10 The Web page example for owa_util.signature (version 1).<br />
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OWA_UTIL.SIGNATURE (VERSION 2) The owa_util.signature (version 2) utility procedure creates a signature line at the bottom of the document that will timestamp the page. In addition, it will include a hypertext link that allows the source code to be viewed for this page. Parameters: cname(in) • cname—Name of the procedure displaying the source code when a hypertext link is clicked on (varchar2). Listing 8.22 shows an example of the owa_util.signature (version 2) utility procedure. Listing 8.22 The owa_util.signature (version 2) utility procedure. create or replace procedure signa1 as begin htp.htmlOpen; htp.headOpen; htp.title('Oracle Webserver owa_util.signature(cname)'); htp.header(1,'Oracle WebServer owa_util.signature(cname) Example'); htp.headClose; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 'sigform'); htp.print('Click on the Image to submit Form'); htp.FormImage('flamingo','/ows-img/flamingo.gif'); htp.nl; htp.FormClose; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/281-286.html (4 of 5)4/03/2005 6:16:00<br />
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owa_util.signature('signa1'); htp.bodyClose; htp.htmlClose; end; / show errors<br />
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Listing 8.23 displays the HTML code generated from the owa_util.signature (version 2) utility procedure. Listing 8.23 The HTML source code generated from the owa_util.signature (version 2) utility procedure. <HTML> <HEAD> <TITLE>Oracle Webserver owa_util.signature(cname)</TITLE> <H1>Oracle WebServer owa_util.signature(cname) Example</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/sigform" METHOD="POST"> Click on the Image to submit Form <INPUT TYPE="image" NAME="flamingo" SRC="/ows-img/flamingo.gif"> <BR> </FORM> <HR> This page was produced by the<br />
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<B>Oracle Web Agent</B> on October 15, 1996 09:00 AM<BR> <A HREF="/ows-bin/owa/owa_util.showsource?cname=signa1" rel="nofollow"> View PL/SQL source code</A> </BODY> </HTML> The Web page created from this code is depicted in Figure 8.11.<br />
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Figure 8.11 The Web page example for owa_util.signature (version 2). Clicking on the hypertext link View PL/SQL source code will display the Web page shown in Figure 8.12.<br />
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Figure 8.12 Source code for the owa_util.signature (version 2) example.<br />
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OWA_UTIL.STATUS_LINE A call to the owa_util.status_line procedure returns an HTTP status code to the browser. This call must precede all htp.print and htp.prn calls in order for the status code to be sent as part of the HTTP header. Otherwise, it would be assumed to be content data. The HTTP header can be closed by setting the parameter bclose_hdr to TRUE, which causes two newlines to be sent. Parameters: nstatus(in), cdesc(in), bclose_hdr(in) • nstatus—HTTP status code being returned to the client (integer). • cdesc—Description of the status code (varchar2). Default is NULL. • bclose_hdr—Setting that indicates whether the HTTP header should be closed (boolean). Default is TRUE.<br />
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OWA_UTIL.TABLEPRINT The owa_util.tableprint procedure displays an Oracle table in a Web page. This procedure is very easy to call and use, but it will not support tables with long raw columns. It returns a TRUE or FALSE boolean, indicating if there are additional rows remaining beyond the value file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/286-290.html (2 of 5)4/03/2005 6:16:01<br />
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defined for parameter nrow_max. In addition, this utility can specify individual columns to be displayed. For example: ignore_more := owa_util.tablePrint('dba_tables', 'BORDER', OWA_UTIL.PRE_TABLE, 'table_name, owner, tablespace_name'); This call would display only the columns called table_name, owner, and tablespace_name in the DBA_TABLE table. Parameters: ctable(in), cattributes(in), ntab_type(in), ccols(in), cclauses(in), ccol_aliases(in), nrow_min(in), nrow_max(in) • ctable—Name of the table to be displayed (varchar2). • cattributes—HTML attributes that define the page (varchar2). Default is NULL. • ntab_type—Table type that pertains to your browser’s capabilities. That is, if your browser does not support HTML tables, then the pre_table type must be used. The value can be html_table or pre_table. Default is owa_util.html_table. • ccols—Column names you wish to display (varchar2). The default is *, which will display all columns in the table. You may also specify individual column names to be printed. • cclauses—DML clause where you specify which rows to retrieve, such as ‘where region=69 order by zone’ (varchar2). Default is NULL. • ccol_aliases—Alias names associated with the columns retrieved (varchar2). Default is NULL. • nrow_min—Minimum number of rows to print (integer). Default is zero. • nrow_max—Maximum number of rows to print (integer). Default is NULL. Listing 8.24 shows a working example of the owa_util.tableprint procedure. Listing 8.24 The owa_util.tableprint procedure. create or replace procedure tableprint as ignore_more boolean; begin htp.htmlOpen; htp.headOpen; htp.header(1,'Oracle WebServer'); htp.header(1,'tablePrint example','C'); htp.headClose; htp.bodyOpen; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/286-290.html (3 of 5)4/03/2005 6:16:01<br />
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ignore_more := owa_util.tablePrint('dba_tables', 'BORDER', OWA_UTIL.PRE_TABLE); htp.FormClose; htp.bodyClose; htp.htmlClose; end; Listing 8.25 shows the HTML generated from the owa_util.tableprint procedure. Listing 8.25 The HTML source code generated from the owa_util.tableprint procedure. <HTML> <BODY> <PRE> ----------------------------------------------------------------------------------------------| HOST_NAME | IP_ADDRESS | CUST_NAME | OS_TYPE | OS_VERSION | ORACLE_CSI_NBR | DBA_PAGER_NBR | ----------------------------------------------------------------------------------------------| | | | | | | | ----------------------------------------------------------------------------------------------</PRE> <BR> <BR> </FORM> </BODY> </HTML> The Web page created from this code is depicted in Figure 8.13.<br />
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Figure 8.13 The Web page example for the owa_util.tableprint procedure.<br />
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Summary The OWA utilities described in this chapter add another dimension to the functionality of the hypertext procedures and functions included with Oracle WebServer. Web application developers have been given numerous options to enhance the usefulness and capabilities of their applications. Effective and efficient interaction between the Web and corporate data repositories will further the benefits to business file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch08/286-290.html (4 of 5)4/03/2005 6:16:01<br />
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CHAPTER 9 Oracle WebServer And PL/SQL While many books have been written about programming with PL/SQL, this chapter is devoted to the PL/SQL statements commonly used when creating Web pages for Oracle WebServer. As we discussed in the previous chapter, a standard library of HTML function calls are used to create the Web screen images, but these calls are usually embedded within PL/SQL code. PL/SQL is the acronym for Procedural Language/Structured Query Language and is a proprietary language created by Oracle for use with Oracle databases. In syntax, PL/ SQL is an ADA-like procedural language used to create a variety of online Oracle applications. Like any language, PL/SQL allows for control statements (if-then-else), looping (while-do, repeat-until), declaration of variables, and error handling. In addition, PL/SQL contains many pretested built-in functions (BIFs) that greatly improve the usefulness of the language. Like most procedural languages, PL/SQL is compiled prior to runtime, and Oracle allows for the precompiled executables to be stored procedures in a database. The general construct of PL/SQL code is the block. All blocks within PL/SQL contain three sections: Declare, Begin, and Exception.<br />
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PL/SQL is a highly structured language that consists of three primary sections: the Declare section, the Begin section, and the Exception section. Within the first two main sections, Declare and Begin, we find the majority of syntax of the PL/SQL language. Declare Section The Declare section always begins with the word declare and ends with the word begin. The Declare section defines the local variables to be referenced within the program. The Declare section consists of variable and cursor declarations.<br />
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Variable Declaration Variable declarations include all string, numeric, and binary types. The following declarations are examples of scalar declarations: • cust_num—INTEGER(4) := 100; • person_num—custnum%type; • tran_amount—CONSTANT NUMBER(4,2) := 100;<br />
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Note: The second declaration states that person_num has the same definition as the cust_num variable. This shorthand syntax is the equivalent of the COBOL redefines clause.<br />
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Cursor Declaration In addition to variable declarations, cursor declarations are generally included in the Declare section. Other procedural languages use cursor statements only for situations where multiple rows will be retrieved; PL/SQL may use cursor statements for multiple and single row retrievals from an Oracle database. Looking at the declaration section, it is impossible to tell if the cursor declaration will retrieve a single row or multiple rows from an Oracle database. Listing 9.1 shows an example of a cursor declaration from a WebServer stored procedure. Listing 9.1 A sample PL/SQL declare section. create or replace procedure s10(host_name_in in varchar2) as . . . cursor c1 is select responsibility, a.dba_name, dept_name, phone_nbr, e_mail, file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/291-295.html (2 of 4)4/03/2005 6:16:01<br />
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office_hrs, home_phone_nbr from dba_host a, dba b where host_name = rtrim(host_name_in) and a.dba_name = b.dba_name; host_rec c1%ROWTYPE; BEGIN htp.bodyOpen; . . . The Begin Section Next, we see the section that starts after the begin statement. This section is called the executable section of PL/SQL, and this is where the main PL/SQL processing takes place. This section is analogous to the Procedure Division in a COBOL program. The main processing takes place within the executable section, and includes all of the processing necessary to build and display the WebServer page for the end user. Looping In PL/SQL With Oracle WebServer, there are two loop structures available when you need to retrieve a series of rows from a table and display the results on a Web page. While PL/ SQL supports for loops, while loops, and loop-until-exit structures, WebServer developers most commonly use for loops or loop-until-exit to retrieve Oracle rows and display them on a Web page. Listing 9.2 shows a WebServer example that creates a checkbox list that contains all of the column names in the dba_tables view. Listing 9.2 Example of for loop WebServer row retrieval. create or replace procedure formcheckbox (tab_name in varchar2) is cursor cols is select column_name from dba_tab_columns where table_name = upper(tab_name); BEGIN . . . . for crec in cols loop htp.formCheckbox('COLS',crec.column_name); htp.print(crec.column_name); htp.nl; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/291-295.html (3 of 4)4/03/2005 6:16:01<br />
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end loop; . . . . end; In Listing 9.2, we see that a cursor called cols is declared and referenced in the for loop, such that each row returned (in this case, the column_names from the dba_tables view) is mapped into a checkbox using the htp.formCheckbox call. Also, PL/SQL can be used to set a loop-until-exit loop, where the PL/SQL code must expressly request an exit from the loop. The basic syntax of the PL/SQL loop-untilexit is: counter := 0; loop If counter > 100 then exit; end if; counter := counter + 1; end loop; PL/SQL provides several methods for exiting a loop-until-exit loop. In the following example, the PL/SQL exit when is used to terminate the loop: declare cursor c1 as. ... BEGIN loop fetch c1 into. .. exit when c1%NOTFOUND; end loop close c1<br />
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In Oracle WebServer, the PL/SQL loop-until-exit structure can be used to retrieve a series of rows from an Oracle table. In Listing 9.3, multiple rows are selected from the table called DBA and displayed on a Web page. Listing 9.3 Example of the PL/SQL loop-until-exit syntax. create or replace procedure s10(host_name_in in varchar2) as responsibility varchar2(20); dba_name varchar2(20); dept_name varchar2(20); phone_nbr varchar2(20); e_mail varchar2(20); office_hrs varchar2(20); home_phone_nbr varchar2(20); counter integer := 0; cursor c2 is select responsibility, a.dba_name, dept_name, phone_nbr, e_mail, office_hrs, home_phone_nbr from dba_host a, dba b where host_name = rtrim(host_name_in) and a.dba_name = b.dba_name; dba_rec<br />
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BEGIN htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's10'); htp.htmlOpen; htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; htp.header(2,'DBA name Responsibility phone office_hrs home phone : '); htp.nl;<br />
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open c2; loop counter := counter + 1; fetch c2 into dba_rec; EXIT WHEN c2%NOTFOUND; htp.FormText('dba_name'||counter,10,50,dba_rec.dba_name); htp.FormText('responsibility'||counter,10,50,dba_rec.responsibility); htp.FormText('dba_phone'||counter,10,50,dba_rec.phone_nbr); htp.FormText('dba_e_mail'||counter,30,50,dba_rec.e_mail); htp.FormText('dba_office_hrs'||counter,10,50,dba_rec.office_hrs); htp.FormText('home_phone_nbr'||counter,10,50,dba_rec.home_phone_nbr); htp.nl; htp.nl; end loop; close c2; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors<br />
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PL/SQL And Stored Procedures As objects such as stored procedures and triggers become more popular, more application code will move away from external programs and into the database engine. Oracle has been encouraging this approach in anticipation of the object-oriented features of Oracle version 8. However, the Oracle DBA must be conscious of the increasing memory and disk storage demands of stored procedures, and carefully plan for the days when all of the database access code resides within the database. Today, most Oracle databases have only a small amount of code in stored procedures, but this is rapidly changing. There are many compelling benefits to putting all Oracle SQL inside stored procedures. These benefits include: • Better performance—Stored procedures are loaded once into the SGA and remain there unless they become paged out. Subsequent executions of the stored procedure are far faster than external code. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/295-299.html (2 of 3)4/03/2005 6:16:02<br />
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• Coupling of data with behavior—Relational tables can be coupled with the behaviors associated with them by using naming conventions. For example, if all behaviors associated with the employee table are prefixed with the table name (e.g., EMPLOYEE.hire,EMPLOYEE.give_raise), then the data dictionary can be queried to list all behaviors associated with a table (e.g., select * from dba_objects where owner = ‘EMPLOYEE’) and code can be readily identified and reused. • Isolation of code—Because all SQL is moved out of the external programs and into stored procedures, the application programs become nothing more than calls to stored procedures. As such, it becomes very simple to swap out one database and swap in another. • Encapsulation—Code resides in the database instead of in external programs. With the proper use of Oracle packages, stored procedures can be logically grouped together into a cohesive framework of SQL statements. • More flexibility—By keeping all database access inside Oracle packages, the applications contain no SQL and become little more than a set of calls to the stored procedures. As such, the application is insulated from the database, and it becomes very easy to migrate the application to another platform or database product.<br />
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Note: Oracle System Global Area (SGA) is one of the foremost reasons why stored procedures function faster than traditional code. After a procedure has been loaded into the SGA, it will remain there until it is paged out of memory. Items are paged out based on a least-recently-used algorithm. Once loaded into the RAM memory of the shared pool, the procedure will execute very quickly. The trick is to prevent pool-thrashing while many procedures compete for a limited amount of shared pool memory.<br />
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PL/SQL Stored Procedures And Packages Oracle also provides a construct called a package. Essentially, a package is a collection of functions and stored procedures that can be organized in a variety of ways. For example, functions and stored procedures for employees can be logically grouped together in an employee package as follows: CREATE PACKAGE employee AS FUNCTION compute_raise_amount (percentage NUMBER); PROCEDURE hire_employee(); PROCEDURE fire_employee(); PROCEDURE list_employee_details(); END employee; Here, we have encapsulated all employee behaviors into a single package that will be added to Oracle’s data dictionary. If we force our programmers to use stored procedures, the SQL moves out of the external programs and the application programs become nothing more than a series of calls to Oracle stored procedures.<br />
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Note: For Oracle WebServer, it is a good idea to use a package to encapsulate all stored procedures associated with a specific Web page. For example, Web page display, update, and delete procedures could be combined into a single package, and the package name would be the name of the Web page.<br />
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Tuning PL/SQL PL/SQL is commonly used within Oracle’s SQL*Forms application framework. Recently, the popularity of PL/SQL for non-SQL*Forms applications has re-emerged because of the benefits of using Oracle stored procedures—which must be written with PL/SQL. PL/SQL offers the standard language constructs including looping, if statement structures, assignment statements, and error handling. However, there are several problems with PL/SQL, each of which warrants special attention. PL/SQL offers two types of SQL cursors, the explicit cursor and the implicit cursor. Explicit cursors are manually declared in the PL/SQL: DECLARE CURSOR C1 IS select last_name from customer where cust_id = 1234; However, it is possible to issue the SQL statement directly in PL/SQL without specifying the cursor name. When this happens, Oracle opens an implicit cursor to handle the request. Implicit cursors create a tremendous burden for Oracle, as the implicit cursor must always reissue a fetch command to ensure that only a single row was returned by the query. This will double the amount of fetch statements for the query. The moral is simple: Always be sure that you declare all cursors in your PL/ SQL. Most savvy Oracle developers are aware that PL/SQL allows certain types of correlated subqueries to run much faster than a traditional Oracle SQL query. For example, consider a situation where a bank maintains two tables: a GENERAL_LEDGER table and a TRANSACTION table. At the end of the banking day, each check in the TRANSACTION table is applied to the GENERAL_LEDGER table, making the requisite deductions from the account_balance column. Furthermore, let’s assume that the GENERAL_LEDGER table contains 100,000 rows and the TRANSACTION table processes 5,000 checks each day. A traditional SQL query to accomplish the updating of the account_balance column of the<br />
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GENERAL_LEDGER table would involve a correlated subquery, as shown in Listing 9.4. Listing 9.4 A traditional correlated subquery. update GENERAL_LEDGER set account_balance = account_balance (select check_amount from TRANSACTION where TRANSACTION.account_number = GENERAL_LEDGER.account_number) where exists (select 'x' from TRANSACTION where TRANSACTION.account_number = GENERAL_LEDGER.account_number); As you may recall, a correlated subquery involves executing the subquery first and then applying the result to the entire outer query. In this case, the inner query will execute 5,000 times, and the outer query is executed once for each row returned from the inner query. This Cartesian product problem has always been a problem for correlated subqueries. Now, consider the identical query written in PL/SQL, as shown in Listing 9.5. Listing 9.5 A correlated subquery using PL/SQL. DECLARE CURSOR c1 is select account_number, check_amount from TRANSACTION ; keep_account_number keep_check_amount<br />
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number; number;<br />
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BEGIN OPEN C1; LOOP fetch C1 into keep_account_number, keep check_amount; exit when C1%NOTFOUND; update GENERAL_LEDGER set account_balance = account_balance - keep_check_amount where account_number = keep_account_number; END LOOP; END; In Listing 9.5 we see that each check amount is retrieved in a separate transaction and fetched into cursor C1. For each check_amount, the balance is applied to the GENERAL_LEDGER row, one at a time.<br />
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Passing Parameters To Oracle Stored Procedures From The Web As we know from previous chapters, PL/SQL is created inside Oracle stored procedures. A stored procedure may accept parameters if the Web page is passing a value to a subsequent Web page, as follows: http://www.oracle.com:8880/ows-bin/owa/customer.entry?customer=IBM<br />
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In this example, the package called customer is scanned to invoke a procedure called entry. The entry procedure is then invoked with the input parameter customer set to the value IBM. If we take a look at customer.entry, it should become clear how the variables are passed into the stored procedure. The entry procedure is defined to accept a parameter called customer, as seen in the following code: create or replace package customer as procedure entry; end; / show errors create or replace package body customer as procedure entry (customer in varchar2(30)) as . . . end; So, it appears that the name of the parameter and the value of the parameter must be specified in the URL that calls the WebServer page. How then, do we get these values into the URL call? If we start by taking a look at the following native HTML, we can see how the HTML <INPUT> tag can be used to accept a value for the customer parameter. We can also see that the <FORM> tag is used to specify the URL for the target WebServer page: <FORM METHOD="POST" ACTION="http://www.oracle.com:8880/ows-bin/owa/customer.entry"> <INPUT TYPE="text" NAME="customer"><P> Enter the customer name here: <INPUT TYPE="submit" VALUE="Submit Query"> <P> </FORM> When using WebServer, the following code could be used to create an input form so the user can enter the customer name and an anchor to transfer to the customer.entry page when the anchor was mashed: formtext('customer name ', 'customer'); htp.tabledata(htf.anchor('customer.entry?customer='||customer, 'Display this customer')); To complete the illustration, look at how the customer.entry procedure might appear. Here we see a simple process where customer is received and used to retrieve a single row from the CUSTOMER_TABLE. The htp.print command is then used to display the number_of_orders column. create or replace procedure entry (customer in varchar2) is number_of_orders integer; BEGIN select num_orders into number_of_orders from where cust_name=customer;<br />
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CUSTOMER_TABLE<br />
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htp.print(customer||' has placed '||to_char(number_of_orders)||<br />
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' this year.'); END; Now that we understand how parameters are initially passed to a Web page, let’s take a look at how data items are passed between Web pages in an Oracle application.<br />
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Passing Parameters Between PL/SQL Stored Procedures Another time parameters are passed to a PL/SQL stored procedure is when an update routine is called from a WebServer page. When using WebServer, it is customary to pass the rowid of the row to be changed and a list of all the row values to an update procedure. This update procedure will check to ensure that the row has not changed since it was originally retrieved (we are not holding locks), update the row, check the return code, and return the appropriate message to the originating Web page. In the following example, a single row with seven columns is retrieved from Oracle. Also, note that the first item in the select statement grabs the rowid for the row. Now that we have the rowid, we can look at how the rowid can be passed as a parameter to an update routine. Essentially, PL/SQL allows for two methods: • Pass the rowid as an external parameter using htp.anchor: htp.tabledata(htf.anchor('update_host?my_rowid='||host_rec.rowid, 'Update this host')); • Store the rowid using htp.formhidden, and transfer to the update routine using htp. formsubmit: htp.formhidden('my_rowid', my_rowid); select * into hostrec from host where host_name = my_rowid; htp.tableOpen; formtext('host name ', 'host_name', hostrec.host_name); formtext('IP address ', 'ip_address', hostrec.ip_address); htp.tableClose;<br />
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htp.formsubmit('p_action', cvalue => 'Update'); htp.formsubmit('p_action', cvalue => 'Delete'); To see how each method works, let’s examine a complete stored procedure that uses htp.anchor to transfer to the update routine with the rowid of the row that will be updated. Listing 9.6 displays the use of htp.anchor to pass a rowid to an update procedure. Listing 9.6 Using htp.anchor to pass a rowid to an update procedure. create or replace procedure s10a(host_name_in in varchar2) as BEGIN htp.htmlOpen; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's10'); htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; for host_rec in ( select rowid, host_name, ip_address, cust_name, os_type, os_version, oracle_csi_nbr, dba_pager_nbr from host where host_name = rtrim(host_name_in)) loop htp.tabledata(htp.anchor('update_host?my_rowid='||host_rec.rowid, 'Update this host')); htp.nl; htp.nl; htp.print('Host Name: '); htp.FormText('host_name',10,50,host_rec.host_name); htp.print('IP address: '); htp.FormText('ip_address',20,50,host_rec.ip_address); htp.print('Customer_name: '); htp.FormText('cust_name',10,50,host_rec.cust_name); htp.print('Operating System: '); htp.FormText('os_type',10,50,host_rec.os_type); htp.print('Operating System version: '); htp.FormText('os_version',10,50,host_rec.os_version); htp.print('Oracle CSI Number: '); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/303-307.html (2 of 4)4/03/2005 6:16:03<br />
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htp.FormText('oracle_csi_nbr',10,50,host_rec.oracle_csi_nbr); htp.print('DBA pager number: '); htp.FormText('dba_pager_nbr',10,50,host_rec.dba_pager_nbr); end loop; htp.nl; htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; It is important to note how the rowid is passed to the update routine. In Listing 9.6, the htp.anchor tag has the name of the routine (update_host) concatenated with the rowid of the current row. The current row was retrieved from the Oracle database and placed into the variable named my_rowid. Of course, there are many ways to accomplish this type of parameter passing, and this text does not have enough pages to illustrate every possible technique. Another popular method for passing parameters to a procedure is to use the htp.formhidden command. To illustrate, consider Listing 9.7. Listing 9.7 Using htp.formhidden with htp.formsubmit to pass a rowid to a stored procedure. create or replace procedure update_host (my_rowid in rowid, msg in varchar2 default NULL) is hostrec host%rowtype; BEGIN htp.htmlOpen; htp.headOpen; htp.title('Test'); htp.headClose; htp.bodyOpen; if (msg is not null) then htp.bold(msg); end if; htp.formopen('do_update'); htp.formhidden('my_rowid', my_rowid); select * into hostrec from host where host_name = my_rowid; htp.tableOpen; formtext('host name ', 'host_name', hostrec.host_name); formtext('IP address ', 'ip_address', hostrec.ip_address); htp.tableClose; htp.formsubmit('p_action', cvalue => 'Update'); htp.formsubmit('p_action', cvalue => 'Delete'); htp.formReset; htp.formClose; htp.bodyClose; htp.htmlClose; end; In Listing 9.7, we see that the rowid is saved by calling htp.formhidden, while the transfer to the update routine is handled by htp.formsubmit. The htp.formsubmit statement in Listing 9.7 displays file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/303-307.html (3 of 4)4/03/2005 6:16:03<br />
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two buttons: Update and Delete. When either of these buttons is pressed, the do_update routine is called because it was specified in the htp.formopen statement. Now, you are probably asking yourself, “We have passed the rowid, but what about the column data that will be updated?” As we know, in PL/SQL, every parameter passed to a procedure must be defined in the Declare section. For rows that contain dozens of columns, it can be very cumbersome to write an update routine that accepts a parameter for each column to be updated. For example, the routine shown in Listing 9.8 could be used to update a customer table. Listing 9.8 Update a customer table by passing each parameter. create or replace procedure update_customer (my_rowid in rowid, customer_name_parm in varchar2, customer_street_parm in varchar2, customer_zip_parm in integer, customer_city_parm in varchar2, customer_state_parm in varchar2, customer_status_parm in varchar2 msg in varchar2 default NULL) is hostrec customer%rowtype; BEGIN htp.htmlOpen; . . . update customer set customer_name customer_street customer_city customer_zip customer_state customer_status where<br />
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= = = = = =<br />
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customer_name_parm, customer_street_parm, customer_city_parm, customer_zip_parm, customer_state_parm, customer_status_parm<br />
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rowid = my_rowid; . . . htp.htmlClose; end;<br />
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The problem of passing large numbers of input parameters becomes even more confounding when we are passing multiple rows of data to a PL/SQL routine for updating. Fortunately, Oracle has provided a package called owa_parms to simplify the passing of parameters between WebServer pages. The owa_parms utility allows the column values to be stuffed into a single array and passed as an associative array, all within a single parameter.<br />
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Note: For further details about owa_parms, see Chapter 8, WebServer’s OWA Utilities.<br />
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Here’s how owa_parms works. When a row is retrieved from Oracle, the owa_parms.register procedure is used to store all of the values into a single associative array. The name of this array is then manipulated in the PL/SQL stored procedure that performs the updating. In PL/SQL, we can create user-defined data types, and these data types can be a single value, a list of values, or an array of values. In Listing 9.9, htp.formhidden is called once for each column displayed on the Web page. Note the use of a small procedure called formfield. Each time the formfield procedure is called, the variable is displayed on the Web page (using htp.tableData) and the column values are passed using the htp.formhidden procedure. Listing 9.9 Passing table data into an associative array for passing to other procedures. create or replace procedure formfield (p_label p_name p_value<br />
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in varchar2, in varchar2, in varchar2) is<br />
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BEGIN htp.tableRowOpen; htp.tableData (p_label); htp.tableData(htf.formHidden('p_name', p_name)|| htf.formText(p_value, 10, 50, cvalue => p_value)); htp.tableRowClose; end;<br />
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create or replace procedure update_form (host_name_in in varchar2) is BEGIN htp.formOpen('do_update'); for host_rec in ( select rowid, host_name, ip_address, cust_name, os_type, os_version, oracle_csi_nbr, dba_pager_nbr from host where host_name = rtrim(host_name_in)) loop htp.tableData(htf.anchor('update_host?my_rowid='||host_rec.rowid, 'Update this host')); htp.nl; htp.nl; htp.print('Host Name: '); formfield('host_name','p_host_name',host_rec.host_name); htp.print('IP address: '); formfield('ip_address','p_ip_address',host_rec.ip_address); htp.print('Customer Name: '); formfield('cust_name','p_cust_name',host_rec.cust_name); htp.print('Operating System: '); formfield('os_type','p_os_type',host_rec.os_type); htp.print('Operating System version: '); formfield('os_version','p_os_version',host_rec.os_version); htp.print('Oracle CSI Number: '); formfield('oracle_csi_nbr','p_csi_nbr',host_rec.oracle_csi_nbr); htp.print('DBA pager number: '); formfield('dba_pager_nbr','p_dba_pager_nbr',host_rec.dba_pager_nbr); end loop; htp.nl; htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors; Figure 9.1 displays the Web page generated from the code in Listing 9.9.<br />
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Figure 9.1 A sample data input form using htp.formhidden. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/307-311.html (2 of 4)4/03/2005 6:16:04<br />
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As we can see, once the values are stored in the array, they can be passed to another procedure where they can be interrogated and used to update the Oracle database. To see how this works, take a look at Listing 9.10, which shows how the receiving routine accepts the array. Listing 9.10 The process of accepting parameters from an associative array. procedure update_customer ( p_rowid in rowid, p_name in owa_parms.array, p_values in owa_parms.array) is BEGIN owa_parms.register (p_name, p_values); ... ... end; This routine accepts three parameters: the rowid of the row to be updated, an array of type owa_parms.array that contains the name of the array item, and another array of type owa_parms.array that holds the list of column values. The owa_parms.register function is then invoked. We are now ready to update our Oracle database with the new column values. Let’s start by examining the procedure that receives the parameters and issues the sql update statement, as shown in Listing 9.11. Listing 9.11 The process of updating Oracle based on data in an associative array. procedure do_update ( p_rowid in rowid, p_name in owa_parms.array, p_values in owa_parms.array) is BEGIN owa_parms.register (p_name, p_values); update host set host_name ip_address cust_name os_type os_version oracle_csi_nbr dba_pager_nbr where rowid<br />
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= = = = = = = =<br />
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owa_parms.get('p_host_name'), owa_parms.get('p_ip_address'), owa_parms.get('p_cust_name'), owa_parms.get('p_os_type'), owa_parms.get('p_os_version'), owa_parms.get('p_oracle_csi_nbr'), owa_parms.get('p_dba_pager_nbr') p_rowid;<br />
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htp.FormClose; htp.bodyClose; htp.htmlClose; end; Now, let’s take a careful look at what is happening in the procedure shown in Listing 9.11. We see that each column of the desired row is being assigned to the value of owa_parms.get(‘name_value’). The owa_parms. get function accepts the name of an array item and returns the value associated with the name when it was stored using the owa_parms.register procedure. To thoroughly understand how the owa_parms package works, you may want to take a look at the source code for the package. It is stored in the file owa_parms.sql.<br />
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Note: The owa_parms package is only available with WebServer version 2.1 and later. If you do not have it, you can download it from http://www.oracle.com. Once downloaded, the package should reside on your WebServer host in $ORACLE_HOME/ows2/admin/owa_ parms.sql.<br />
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Managing Oracle I/O Using PL/SQL And WebServer While input/output operations are very similar between PL/SQL in SQL*Forms and WebServer, there are some important differences, especially in the manner in which Oracle data is displayed to the end user. This section will explore various ways of performing input against your Oracle database and mapping the retrieved data back to your Web page. Returning A Single Row From An Oracle Database Into A Web Page When Oracle is asked to return a single row value from a database, it is a simple matter to display the columns on a Web page. For example, consider the PL/SQL code shown in Listing 9.12, where a single row is returned from the host table and displayed on a Web page. Listing 9.12 Returning a single row into a Web page. create or replace procedure s10a(host_name_in in varchar2) as BEGIN htp.htmlOpen; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's10'); htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; htp.FormSubmit('s10uh','Update Host Information'); htp.nl; htp.nl;<br />
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for host_rec in ( select host_name, ip_address, cust_name, os_type, os_version, oracle_csi_nbr, dba_pager_nbr from host where host_name = rtrim(host_name_in)) loop htp.print('Host Name: '); htp.formText('host_name',10,50,host_rec.host_name); htp.print('IP address: '); htp.formText('ip_address',20,50,host_rec.ip_address); htp.print('Customer_name: '); htp.formText('cust_name',10,50,host_rec.cust_name); htp.print('Operating System: '); htp.formText('os_type',10,50,host_rec.os_type); htp.print('Operating System version: '); htp.formText('os_version',10,50,host_rec.os_version); htp.print('Oracle CSI Number: '); htp.formText('oracle_csi_nbr',10,50,host_rec.oracle_csi_nbr); htp.print('DBA pager number: '); htp.formText('dba_pager_nbr',10,50,host_rec.dba_pager_nbr); end loop; htp.nl; htp.nl; htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; Note that the htp.formText function is used in Listing 9.12 to create the data input screen. Listing 9.13 displays the HTML source code generated from the code in Listing 9.12. Listing 9.13 The HTML resulting from htp.formText. <HTML> <BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <HEAD> <TITLE>s10</TITLE> <H1>Oracle information database</H1> <H1 ALIGN="C">Host Display</H1> </HEAD> <TD><A HREF="update_host?my_rowid=0000000F.0000.0005" rel="nofollow"> Update this host</A></TD> <BR> <BR> Host Name: <INPUT TYPE="text" NAME="host_name" SIZE="10" MAXLENGTH="50" file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/312-317.html (2 of 5)4/03/2005 6:16:05<br />
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VALUE=""> IP address: <INPUT TYPE="text" NAME="ip_address" SIZE="20" MAXLENGTH="50" VALUE=""> Customer_name: <INPUT TYPE="text" NAME="cust_name" SIZE="10" MAXLENGTH="50" VALUE=""> Operating System: <INPUT TYPE="text" NAME="os_type" SIZE="10" MAXLENGTH="50" VALUE="Solaris"> Operating System version: <INPUT TYPE="text" NAME="os_version" SIZE="10" MAXLENGTH="50" VALUE="2.5"> Oracle CSI Number: <INPUT TYPE="text" NAME="oracle_csi_nbr" SIZE="10" MAXLENGTH="50" VALUE="1234567"> DBA pager number: <INPUT TYPE="text" NAME="dba_pager_nbr" SIZE="10" MAXLENGTH="50" VALUE=""> <BR> <BR> </FORM> </BODY> </HTML> Listing 9.13 shows that htp.formText created <INPUT> tags. Figure 9.2 displays the Web page created from the HTML code in Listing 9.13.<br />
<br />
Figure 9.2 A Web page that uses htp.formText. WebServer provides other methods for displaying row data. Another way to display the data is by using the htp. tableData procedure, as shown in Listing 9.14. Listing 9.14 Returning a single row into a Web page using htp.tableData. create or replace procedure formfield (p_label p_name p_value<br />
<br />
in varchar2, in varchar2, in varchar2) is<br />
<br />
BEGIN htp.tableRowOpen; htp.tableData (p_label); htp.tableData(htf.formHidden('p_name', p_name)|| htf.formText(p_value, 10, 50, cvalue => p_value)); htp.tableRowClose; end; create or replace procedure update_form (host_name_in in varchar2) is BEGIN htp.formOpen('do_update'); for host_rec in ( select rowid, file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/312-317.html (3 of 5)4/03/2005 6:16:05<br />
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host_name, ip_address, cust_name, os_type, os_version, oracle_csi_nbr, dba_pager_nbr from host where host_name = rtrim(host_name_in)) loop htp.tableData(htf.anchor('update_host?my_rowid='||host_rec.rowid, 'Update this host')); htp.nl; htp.nl; htp.print('Host Name: '); formfield('host_name','p_host_name',host_rec.host_name); htp.print('IP address: '); formfield('ip_address','p_ip_address',host_rec.ip_address); htp.print('Customer Name: '); formfield('cust_name','p_cust_name',host_rec.cust_name); htp.print('Operating System: '); formfield('os_type','p_os_type',host_rec.os_type); htp.print('Operating System version: '); formfield('os_version','p_os_version',host_rec.os_version); htp.print('Oracle CSI Number: '); formfield('oracle_csi_nbr','p_csi_nbr',host_rec.oracle_csi_nbr); htp.print('DBA pager number: '); formfield('dba_pager_nbr','p_dba_pager_nbr',host_rec.dba_pager_nbr); end loop; htp.nl; htp.nl; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / Listing 9.14 is a very important example—it shows the use of a subfunction called formfield that takes the incoming data and nests three htp functions. The structure is as follows: htp.tableData<br />
<br />
(htf.formHidden||htf.formText)<br />
<br />
Note: Remember from Chapter 7 that functions called from within htp procedures use their htf equivalent.<br />
<br />
The formfield subfunction does more than simply display Oracle data on a Web page. The htp.tableData function encapsulates the htf.formHidden and the htf.formText, while htp.formhidden stores the column value into an array. Finally htp.formText is used to display the column value. Listing 9.15 is the HTML that results from the WebServer code displayed in Listing 9.14.<br />
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Listing 9.15 HTML resulting from htp.tableData. <FORM ACTION="do_update" METHOD="POST"> <TD><A HREF="update_host?my_rowid=0000000F.0000.0005" rel="nofollow"> Update this host</A></TD> <BR> <BR> Host Name: <TR> <TD>host_name</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_host_name"> <INPUT TYPE="text" NAME="" SIZE="10" MAXLENGTH="50" VALUE=""></TD> </TR> IP address: <TR> <TD>ip_address</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_ip_address"> <INPUT TYPE="text" NAME="" SIZE="10" MAXLENGTH="50" VALUE=""></TD> </TR> Customer Name: <TR> <TD>cust_name</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_cust_name"> <INPUT TYPE="text" NAME="STARS" SIZE="10" MAXLENGTH="50" VALUE="STARS"> </TD> </TR> Operating System: <TR> <TD>os_type</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_os_type"> <INPUT TYPE="text" NAME="Solaris" SIZE="10" MAXLENGTH="50" VALUE="Solaris"></TD><br />
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</TR> Operating System version: <TR> <TD>os_version</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_os_version"> <INPUT TYPE="text" NAME="2.5" SIZE="10" MAXLENGTH="50" VALUE="2.5"> </TD> </TR> Oracle CSI Number: <TR> <TD>oracle_csi_nbr</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_csi_nbr"> <INPUT TYPE="text" NAME="1234567" SIZE="10" MAXLENGTH="50" VALUE="1234567"></TD> </TR> DBA pager number: <TR> <TD>dba_pager_nbr</TD> <TD><INPUT TYPE="hidden" NAME="p_name" VALUE="p_dba_pager_nbr"> <INPUT TYPE="text" NAME="777-7777" SIZE="10" MAXLENGTH="50" VALUE="777-7777"></TD> </TR> <BR> <BR> </FORM> </BODY> </HTML> Note that the executable HTML is not identical to the HTML generated in Listing 9.13. The use of htp. tableData creates two <INPUT> tags: one for the hidden form values and another to display the input values on the Web page. Returning Lists Of Values From Oracle To A Web Page Returning a list of values to Web pages using PL/SQL is a very simple matter, especially when compared to returning a list of values into a SQL*Form. Unlike SQL*Forms, Web pages allow for an almost infinite number of repeating values to be displayed on a single Web page. Because Web browsers enable the end user to scroll through Web pages, a Web page with 500 rows can be displayed and the end user can simply browse forward and backward through the Web page. This means that developers no longer have to deal with the problem of paging screens and forcing the end user to manually retrieve the next set of repeating data (see Listing 9.16). Listing 9.16 Retrieving multiple rows from Oracle into a Web page. create or replace procedure s10(host_name_in in varchar2) as responsibility dba_name dept_name phone_nbr e_mail office_hrs home_phone_nbr<br />
<br />
varchar2(20); varchar2(20); varchar2(20); varchar2(20); varchar2(20); varchar2(20); varchar2(20);<br />
<br />
counter integer := 0; cursor c2 is select<br />
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responsibility, a.dba_name, dept_name, phone_nbr, e_mail, office_hrs, home_phone_nbr from dba_host a, dba b where host_name = rtrim(host_name_in) and a.dba_name = b.dba_name; dba_rec<br />
<br />
c2%ROWTYPE;<br />
<br />
BEGIN htp.htmlOpen; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's10'); htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; htp.header(2,'DBA name Responsibility phone office_hrs home phone : '); htp.nl;<br />
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e-mail<br />
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open c2; loop counter := counter + 1; fetch c2 into dba_rec; EXIT WHEN c2%NOTFOUND; htp.formText('dba_name'||counter,10,50,dba_rec.dba_name); htp.formText('responsibility'||counter,10,50,dba_rec.responsibility); htp.formText('dba_phone'||counter,10,50,dba_rec.phone_nbr); htp.formText('dba_e_mail'||counter,30,50,dba_rec.e_mail); htp.formText('dba_office_hrs'||counter,10,50,dba_rec.office_hrs); htp.formText('home_phone_nbr'||counter,10,50,dba_rec.home_phone_nbr); htp.nl; htp.nl; end loop; close c2; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 9.17 shows another technique for retrieving multiple rows from Oracle to display on a Web page. Listing 9.17 Retrieving multiple rows from Oracle into a Web page using a for loop. create or replace procedure formcheckbox (tab_name in varchar2) is cursor cols is select file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/317-321.html (3 of 4)4/03/2005 6:16:05<br />
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column_name from dba_tab_columns where table_name = upper(tab_name); BEGIN . . . . for crec in cols loop htp.formCheckbox('COLS',crec.column_name); htp.print(crec.column_name); htp.nl; end loop; . . . . end; As you can see in Listings 9.16 and 9.17, a cursor is used to navigate through the Oracle database, returning one row at a time. As we know, a single SQL statement may return hundreds of rows, and a cursor is used to allow PL/SQL to process the rows sequentially. In the above example, htp.print is called one time for each row returned from the cursor.<br />
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Exception Handling In WebServer Whenever a request is made to an Oracle database, the application must become aware of the status of the request after it has been received by Oracle. (See Figure 9.3.) In Oracle SQL, there are several commonly received error statuses, and these need to be checked by your WebServer application to ensure that your process logic is synchronized with the actual results from the Oracle database. For example, you would not want to issue an sql update statement against a row that was not successfully retrieved from Oracle.<br />
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Figure 9.3 Examining Oracle return codes with PL/SQL. In practice, there are only a few conditions that need to be checked from Oracle, but there may be many unexpected return codes that also need to be checked. It is always a safe practice to perform the following generic check whenever PL/SQL is run against the Oracle database. You can define custom error codes according to the needs of your WebServer application. For example, Listing 9.18 defines a custom error code that raises an exception condition if a certain column retrieved from a table is null. Listing 9.18 Using exception with WebServer PL/SQL. create or replace procedure update_customer(my_rowid in rowid) as address_in address_missing<br />
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varchar(20); EXCEPTION;<br />
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BEGIN select address into my_address from customer_table where rowid = my_rowid; if my_address is NULL then raise address_missing; EXCEPTION when no_data_found then error_web_page(Customer); when bad_field error_web_page(Customer); when others then error_web_page(Customer); end; In Listing 9.18, three conditions are raised: one if the rowid fails to retrieve a customer row, another when the address column is NULL, and a third check for any other unexpected return codes from Oracle. All of these conditions will invoke an error Web page that accepts the error message and terminates processing. When using a WebServer application, it is a good idea to create a Web page specifically for the purpose of displaying unexpected Oracle return codes. While your end users should never see this page, it can be an extremely useful tool for debugging your WebServer application. An error page will also aid in the diagnosis of production problems after your WebServer application has been completed. Listing 9.19 shows PL/SQL WebServer code used to generate a generic error page. Listing 9.19 An error Web page. create or replace procedure error_web_page (error_table is BEGIN<br />
<br />
in varchar2)<br />
<br />
htp.htmlOpen; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 'error_web_page'); htp.headOpen; htp.title('error_web_page'); htp.header(1,'Oracle error display page'); htp.nl; htp.bold('Severe Oracle error encountered on the '); htp.bold(error_table); htp.bold(' table. '); htp.nl; htp.nl; htp.nl; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch09/321-324.html (2 of 3)4/03/2005 6:16:06<br />
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htp.nl; htp.nl; htp.p('I don't think we're in Kansas anymore, Toto. .. '); htp.bodyClose; htp.htmlClose; end; Figure 9.4 is the Web page that displays when the code from Listing 9.19 is invoked from WebServer.<br />
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Figure 9.4 A sample WebServer error page for unexpected return codes. Any proficient PL/SQL programmer will be able to provide a complete listing of all the built-in exception conditions of PL/SQL. For detailed information, see the PL/SQL User’s Guide and Reference by Oracle Corporation.<br />
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Summary Now that we’ve covered the basics of using PL/SQL with Oracle WebServer, we are ready to take a close look at how complete applications are designed with WebServer. The following chapter shows screen structures that can be used on a Web page, including radio buttons, pop-up menu values, and checkboxes. Later, we’ll take a look at advanced WebServer application development techniques.<br />
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CHAPTER 10 Managing WebServer Forms And Security In general, the fundamental nature of online applications does not change simply because the front end resides on a Web page. You still need to define menus, data input fields, pop-up lists, radio buttons, checkboxes, and so on. This chapter assumes that you are familiar with these constructs and focuses on how they are efficiently implemented using WebServer. In addition, general rules for mapping database tables to WebServer applications are addressed, and a method for managing Oracle updates is described. Database security is of primary importance when designing a front end that can be accessed from the Internet. You should take special effort to ensure that unauthorized access is not made to your Oracle database, and you should also take steps to ensure that system performance does not suffer when communicating with the Oracle database. As you know, Web pages are static, and communications are terminated with Oracle each time a Web page is sent to the end user. This chapter discusses how security and access concurrency are managed within WebServer. WebServer forms must be designed so that access concurrency is maintained while providing adequate protection for the Oracle information in your database.<br />
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Basic Form Functions In general, a form on a WebServer application differs from a traditional online screen. Because a WebServer page interacts with both Oracle data and end users, the WebServer page needs special objects for communication, including data input fields, radio buttons, checkboxes, hypertext links, and push buttons. These objects constitute the interface to the WebServer page and enable communication between the Oracle database and the user of the Web page. Data Input Fields Data input fields are displayed on a Web page as empty text boxes. Data input fields can be displayed within Oracle WebServer with either default values or values retrieved from the Oracle database. Developers can control the width of text boxes and the number of characters contained in them, but they cannot control the height of the boxes. Figure 10.1 shows a data input field for a Web page.<br />
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Figure 10.1 Sample screen with data input values.<br />
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NOTE: A data input area is defined using the htp.formText call, but you may also want to use htp.formHidden to store the form values for passing them to an update routine. For a detailed description of the use of these procedures, see Chapter 7, WebServer’s HTP Utilities.<br />
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Multiple Data Input Fields Multiple occurrences of input fields are commonly found when a one-to-many data relationship is displayed on a Web page. For example, a customer page may have repeating groups for each order placed by a customer. Because each customer may place many orders, this one-to-many database relationship will be represented on the Web page as a list of repeating values. There is one significant difference between a Web page list and the type of repeating list that an SQL*Forms user may be accustomed to defining. In a traditional display mode, the application is required to display the data in an 80-character wide by 23-character high display screen, but a Web page has no such constraints. Consequently, where a traditional application would force the end user to press a button marked More to see the next series of values, the Web page expands to the length necessary to display all of the information. This feature of Web pages greatly simplifies the presentation of information. To illustrate, let’s consider the situation where a WebServer application manages environmental information about a Unix server. When the user of the WebServer application enters a server name, a Web page is displayed that shows basic server information, including a list of all the DBAs who support the Oracle databases on that server. (See Figure 10.2.)<br />
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Figure 10.2 Sample screen with repeating data input forms. But how was the screen in Figure 10.2 created? Listing 10.1 shows the PL/SQL that was invoked to create the Web page shown in Figure 10.2. Listing 10.1 Displaying repeating rows in a WebServer page. create or replace procedure s10(host_name_in in varchar2) as responsibility varchar2(20); dba_name varchar2(20); dept_name varchar2(20); phone_nbr varchar2(20); e_mail varchar2(20); office_hrs varchar2(20); home_phone_nbr varchar2(20); counter integer := 0; cursor c2 is select responsibility, a.dba_name, file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/325-330.html (2 of 4)4/03/2005 6:16:07<br />
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dept_name, phone_nbr, e_mail, office_hrs, home_phone_nbr from dba_host a, dba b where host_name = rtrim(host_name_in) and a.dba_name = b.dba_name; dba_rec<br />
<br />
c2%ROWTYPE;<br />
<br />
BEGIN htp.htmlOpen; htp.headOpen; htp.title('s10'); htp.header(1,'Oracle information database'); htp.header(1,'Host Display','C'); htp.headClose; htp.bodyOpen; htp.FormOpen(owa_util.get_owa_service_path || 's10'); htp.formSubmit('s10uh','Update Host Information'); htp.nl; htp.nl; htp.header(1,'DBA Display','C'); htp.headClose; htp.formSubmit('s10ud','Update DBA Information'); htp.nl; htp.nl; htp.header(2,'DBA name Responsibility phone home phone : ');<br />
<br />
e-mail<br />
<br />
office_hrs<br />
<br />
htp.nl; open c2; loop counter := counter + 1; fetch c2 into dba_rec; EXIT WHEN c2%NOTFOUND; htp.formText('dba_name'||counter,10,50,dba_rec.dba_name); htp.formText('responsibility'||counter,10,50,dba_rec.responsibility); htp.formText('dba_phone'||counter,10,50,dba_rec.phone_nbr); htp.formText('dba_e_mail'||counter,30,50,dba_rec.e_mail); htp.formText('dba_office_hrs'||counter,10,50,dba_rec.office_hrs); htp.formText('home_phone_nbr'||counter,10,50,dba_rec.home_phone_nbr); htp.nl;<br />
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htp.nl; end loop; close c2; htp.FormClose; htp.bodyClose; htp.htmlClose; end; Notice how the repeating groups are mapped out to the Web page. The cursor c1 is defined for the select that will return only a single row, while cursor c2 is defined for the query that will return multiple rows. The code then steps into a loop, repeating the htp.formText calls to display each row of information. This loop continues until there are no more rows fetched from Oracle, as indicated by the EXIT WHEN c2%NOTFOUND statement. In this example, the loop executed three times, once for each DBA assigned to work on this server. Of course, the HTML document generated from this loop will not have any indication that a loop was involved in creating the HTML document. Listing 10.2 shows the HTML document generated from the PL/SQL shown in Listing 10.1. Notice that the repeating groups of DBA information use numbers in the data names to uniquely distinguish each field.<br />
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Listing 10.2 HTML displaying repeating Oracle rows. <HTML> <HEAD> <TITLE>s10</TITLE> <H1>Oracle information database</H1> <H1 ALIGN="C">Host Display</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <INPUT TYPE="submit" NAME="s10uh" VALUE="Update Host Information"> <BR> <BR> Host Name: <INPUT TYPE="text" NAME="host_name" SIZE="10" MAXLENGTH="50" VALUE="jacob"> IP address: <INPUT TYPE="text" NAME="ip_address" SIZE="20" MAXLENGTH="50" VALUE="134.221.90.xx"> Customer_name: <INPUT TYPE="text" NAME="cust_name" SIZE="10" MAXLENGTH="50" VALUE="STAN"> Operating System: <INPUT TYPE="text" NAME="os_type" SIZE="10" MAXLENGTH="50" VALUE="Solaris"> Operating System version: <INPUT TYPE="text" NAME="os_version" SIZE="10" MAXLENGTH="50" VALUE="2.5"> Oracle CSI Number: <INPUT TYPE="text" NAME="oracle_csi_nbr" SIZE="10" MAXLENGTH="50" VALUE="1234567"> DBA pager number:<br />
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<INPUT TYPE="text" NAME="dba_pager_nbr" SIZE="10" MAXLENGTH="50" VALUE="777-7777"> <BR> <BR> <BR> <BR> <H1 ALIGN="C">DBA Display</H1> <INPUT TYPE="submit" NAME="s10ud" VALUE="Update DBA Information"> <BR> <BR> <H2>DBA name Responsibility phone e-mail office_hrs home phone : </H2> <BR> <INPUT TYPE="text" NAME="dba_name1" SIZE="10" MAXLENGTH="50" VALUE="burleson"> <INPUT TYPE="text" NAME="responsibility1" SIZE="10" MAXLENGTH="50" VALUE="PRIMARY"> <INPUT TYPE="text" NAME="dba_phone1" SIZE="10" MAXLENGTH="50" VALUE="777-7777"> <INPUT TYPE="text" NAME="dba_e_mail1" SIZE="30" MAXLENGTH="50" VALUE="j111111@ravingo"> <INPUT TYPE="text" NAME="dba_office_hrs1" SIZE="10" MAXLENGTH="50" VALUE="m-f 7-4"> <INPUT TYPE="text" NAME="home_phone_nbr1" SIZE="10" MAXLENGTH="50" VALUE="233-1833"> <BR> <BR> <INPUT TYPE="text" NAME="dba_name2" SIZE="10" MAXLENGTH="50" VALUE="papaj"> <INPUT TYPE="text" NAME="responsibility2" SIZE="10" MAXLENGTH="50" VALUE="BACKUP"> <INPUT TYPE="text" NAME="dba_phone2" SIZE="10" MAXLENGTH="50" VALUE="777-4444"> <INPUT TYPE="text" NAME="dba_e_mail2" SIZE="30" MAXLENGTH="50" VALUE="winner@raving"> <INPUT TYPE="text" NAME="dba_office_hrs2" SIZE="10" MAXLENGTH="50" VALUE="m-f 9-4"> <INPUT TYPE="text" NAME="home_phone_nbr2" SIZE="10" MAXLENGTH="50" VALUE="443-4446"> <BR> <BR> <INPUT TYPE="text" NAME="dba_name3" SIZE="10" MAXLENGTH="50" VALUE="odell"> <INPUT TYPE="text" NAME="responsibility3" SIZE="10" MAXLENGTH="50" VALUE="OTHER"> <INPUT TYPE="text" NAME="dba_phone3" SIZE="10" MAXLENGTH="50" VALUE="551-5554"> <INPUT TYPE="text" NAME="dba_e_mail3" SIZE="30" MAXLENGTH="50" VALUE="5555555@ravingo"> <INPUT TYPE="text" NAME="dba_office_hrs3" SIZE="10" MAXLENGTH="50" VALUE="m-f 5-4"> <INPUT TYPE="text" NAME="home_phone_nbr3" SIZE="10" MAXLENGTH="50" VALUE="555-5536"> <BR> <BR> </FORM> </BODY> </HTML><br />
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Checkboxes As you probably already know, checkboxes are used when you need to display items where more than one item can be selected. In other words, checkboxes may be used in a WebServer form whenever the phrase “check all that applies” is appropriate.<br />
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NOTE: Checkboxes are defined using the htp.formCheckbox call. For a detailed description of the use of this procedure, see Chapter 7, WebServer’s HTP Utilities.<br />
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In the example shown in Figure 10.3, you can see a page where a Web user can choose the columns that they would like to display from a table.<br />
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Figure 10.3 Example of a checkbox with Oracle data values. Notice that in the example shown in Figure 10.3, the values next to each checkbox comes from the dba_tables view inside the Oracle dictionary. The ability of WebServer to query databases and display the results in a checkbox is a very powerful feature. Radio Buttons Radio buttons are used when mutually exclusive items, such as sex, race, nationality, must be chosen. Unlike checkboxes, radio buttons do not allow multiple items to be selected at one time—radio buttons are reserved for “one-or-the-other” type responses. Whenever a radio button is selected, the previously selected radio button is automatically deselected to ensure that only one value is indicated. Figure 10.4 shows a WebServer screen using radio buttons.<br />
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Figure 10.4 Example of a radio button with Oracle data values.<br />
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NOTE: In the example shown in Figure 10.4, the values next to each radio button have been retrieved from an Oracle table. Radio buttons are defined using the htp.formRadio call. For a detailed description of the use of this procedure, see Chapter 7, WebServer’s HTP Utilities.<br />
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Pop-Up Lists Pop-up lists are very useful within WebServer applications and are used to limit the type of information provided by end users, as well as to spare end users from having to manually type in information. Using Oracle WebServer, it is very easy to get values for pop-up lists from Oracle tables, but care needs to be taken not to create excessive processing overhead when retrieving pop-up values. For example, it might be tempting to issue the SQL select distinct customer_type from CUSTOMER while ignoring the fact that the CUSTOMER table may contain millions of rows. While the select distinct technique ensures that only valid values are presented to the Web user, a better technique is to create a temporary Oracle table with the unique values and then refresh this temporary table on a periodic basis. For example, a shell script1 called make_list.sh could be executed once each week to refresh the table values. Listing 10.3 shows how a shell script called make_list.sh might appear. Listing 10.3 A sample Korn shell script to access SQL*Plus. sqlplus scott/tiger <<-end>> /tmp/logfile.lst drop table customer_types; create table customer_types as select distinct customer_type from CUSTOMER order by customer_type; -end<br />
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To ensure that this table is refreshed each week, the following entry could be made into the Unix crontab. A crontab is Unix jargon for chronological table, which is a list of entries in a file that specifies programs and the exact times that each program will be run. In the following example, the program called make_list in the /oracle/sql directory is executed at noon on Sunday: 00<br />
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12 * * 0 /oracle/sql/make_list.sh 2>&1<br />
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When a list of distinct table values resides in an Oracle table, the data can be easily gathered from the table using a cursor. Listing 10.4 shows how a table called HOST is queried to supply the values for the pop-up list. Listing 10.4 Using a pop-up list with WebServer. create or replace procedure s00 as host_name_in varchar2(20); cursor c1 is select host_name from HOST order by host_name; host_rec c1%ROWTYPE; BEGIN htp.htmlOpen; htp.headOpen; htp.title('s00'); htp.preOpen; htp.header(1,' Oracle Information Database'); htp.header(1,' Main Menu','C'); htp.preClose; htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's10'); htp.nl; htp.nl; htp.formHidden('host_name_in', host_name_in); htp.formSelectOpen('host_name_in','Choose the Host:'); open c1; loop fetch c1 into host_rec; EXIT WHEN c1%NOTFOUND; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/333-337.html (2 of 4)4/03/2005 6:16:08<br />
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htp.formSelectOption(host_rec.host_name); end loop; close c1; htp.formSelectClose; htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors Listing 10.5 displays the HTML document created from the Oracle stored procedure shown in Listing 10.4. Listing 10.5 The HTML generated for a pop-up list with WebServer. <HTML> <HEAD> <TITLE>s00</TITLE> <PRE> <H1>Oracle Information Database</H1> <H1 ALIGN="C">Main Menu</H1> </PRE> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <BR> <BR> <INPUT TYPE="hidden" NAME="host_name_in" VALUE=""> Choose the Host:<SELECT NAME="host_name_in"> <OPTION>bobby <OPTION>jung <OPTION>sandbox <OPTION>skinner <OPTION>walden <OPTION>zonker </SELECT> <BR> <BR> </FORM> </BODY> </HTML> Figure 10.5 displays the Web page created from the HTML source code shown in Listing 10.5.<br />
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Figure 10.5 Example of a pop-up list with Oracle data values. Menu Screens With Oracle WebServer, there are many tools that you can use to provide menu choices to end users. Whereas character-based application systems of the 1980s only allowed function keys for transferring between screens, WebServer provides a variety of methods for interscreen travel, including: • • • •<br />
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Push buttons (see htp.formSubmit in Chapter 7) Hypertext links (see htp.anchor in Chapter 7) Graphic links (see htp.formImage in Chapter 7) Image maps (see htp.formImage in Chapter 7)<br />
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As with other GUI application systems, designers need to be careful when choosing end-user options available in WebServer, because it is easy to create overly complicated or badly designed menu screens. Care should be taken to clearly choose the methods used to guide your end users through your application structure. Today’s state-of-the-art menus utilize image maps, whereby a large image (a GIF or JPEG file) is displayed. This image contains the main menu for the application. End users click on areas of the image to indicate to WebServer what information they would like to view. To illustrate this principle, consider the home page for Oracle Magazine, shown in Figure 10.6.<br />
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Figure 10.6 An image map used to create a main menu.<br />
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NOTE: For details on using image maps as menus, see Chapter 7, WebServer’s HTP Utilities.<br />
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Updating The Oracle Database From A Web Page Updating an Oracle database from a Web page is similar to the procedure for updating Oracle data from SQL*Forms. However, there are some unique OWA packages that Oracle provides to assist in this function (see Figure 10.7). In general, the following steps occur when updating an Oracle database from a Web page:<br />
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Figure 10.7 Updating an Oracle database from a WebServer page. 1. The WebServer user indicates a desire to update a row by clicking an htp. anchor tag or an htp.formSubmit button. 2. The WebServer application then invokes the mapless PL/SQL procedure to update the row. A mapless procedure is a stored procedure that does not display a Web page. This procedure updates the row, passing the rowid of the row along with all of the new column values. Then, the update procedure performs the following operations: • Verifies that the row has not been changed by another task since it was originally retrieved. • Updates the row. • Checks the SQLCODE. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/337-340.html (1 of 3)4/03/2005 6:16:09<br />
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• Reinvokes the original Web page, passing a status message for display on the invoking Web page.<br />
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NOTE: WebServer can not issue any long-term row locks against the Oracle database. (See Chapter 11, WebServer Navigation And Concurrency Management.) Therefore, because a subsequent retrieval of the row by another task may have changed the column contents, it is imperative that your WebServer code checks to see if any columns have been updated since your Web page mapped out to the end user. There are several techniques for doing this, all of which involve checking the original row contents against the current row values before updating the row.<br />
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Updating A Single Row Chapter 9 discussed two ways that row information can be passed to an update procedure. In order to update Oracle, you need two things: the rowid and a list of the values to be changed. The update procedure can be invoked by using htp.formSubmit (a push button) or htp.anchor (a hyperlink). In either case, you must pass the required information to the update procedure. Following are the steps for updating Oracle from a Web page: 1. Pass the rowid as an external parameter using htp.anchor, as follows: 'Update this host')); 2. Store the rowid and column values using htp.formHidden, and then transfer to the update routine using htp.formSubmit. 3. When the update routine takes control, it will update the row using the rowid, getting the values for the columns using owa_parms.get. As you know, once name-value pairs are saved into an array with htp.formHidden, they can be passed to another procedure where the pairs can be interrogated and used to update the Oracle database. Listing 10.6 shows the WebServer process of receiving a rowid and name-value pairs and updating the HOST table. Listing 10.6 Updating an Oracle database, based on data in an associative array. procedure update_customer ( p_rowid in rowid, p_name in owa_parms.array, p_values in owa_parms.array) is BEGIN owa_parms.register (p_name, p_values); update host set host_name ip_address cust_name<br />
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= owa_parms.get('p_host_name'), = owa_parms.get('p_ip_address'), = owa_parms.get('p_cust_name'),<br />
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os_type os_version oracle_csi_nbr dba_pager_nbr where rowid ... ... end;<br />
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= = = = =<br />
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owa_parms.get('p_os_type'), owa_parms.get('p_os_version'), owa_parms.get('p_oracle_csi_nbr'), owa_parms.get('p_dba_pager_nbr') p_rowid;<br />
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In Listing 10.6, you can see that each column of the desired row is set equal to owa_parms.get(‘name_value’). The owa_parms.get function accepts the name of an array item and returns the value associated with the name when the htp.formHidden statement is used. To thoroughly understand how the owa_parms package works, you should look at the source code for the package in the $ORACLE_HOME/ows2/admin di rectory.<br />
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Updating Multiple Rows The processing of updating multiple rows from a WebServer page is not trivial. Unlike other tools—such as SQL*Forms—where repeating items can be declared as an array and referenced by it’s subscript, Web pages do not allow the concept of arrays or repeating groups. When repeating rows are mapped to a Web page, they must be given unique names so that they can be referenced by subsequent routines. Listing 10.7 shows how repeating data rows can be given unique names by using a counter. Listing 10.7 Creating distinct column names on a WebServer page. create or replace procedure s10(host_name_in in varchar2) as responsibility varchar2(20); dba_name varchar2(20); dept_name varchar2(20); phone_nbr varchar2(20); e_mail varchar2(20); office_hrs varchar2(20); home_phone_nbr varchar2(20); counter integer := 0; cursor c2 is select responsibility, a.dba_name, dept_name, phone_nbr, e_mail, office_hrs, home_phone_nbr from dba_host a, dba b<br />
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where host_name = rtrim(host_name_in) and a.dba_name = b.dba_name; dba_rec<br />
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c2%ROWTYPE;<br />
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BEGIN htp.htmlOpen; htp.headOpen; htp.title('s10'); htp.header(1,'DBA Display','C'); htp.headClose; htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's10'); htp.formSubmit('s10ud','Update DBA Information'); htp.nl; htp.nl; htp.header(2,'DBA name office_hrs home phone htp.nl;<br />
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Responsibility : ');<br />
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phone<br />
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e-mail<br />
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open c2; loop counter := counter + 1; fetch c2 into dba_rec; EXIT WHEN c2%NOTFOUND; htp.formText('dba_name'||counter,10,50,dba_rec.dba_name); htp.formText('responsibility'||counter,10,50,dba_rec.responsibility); htp.formText('dba_phone'||counter,10,50,dba_rec.phone_nbr); htp.formText('dba_e_mail'||counter,30,50,dba_rec.e_mail); htp.formText('dba_office_hrs'||counter,10,50,dba_rec.office_hrs); htp.formText('home_phone_nbr'||counter,10,50,dba_rec.home_phone_nbr); htp.nl; htp.nl; end loop; close c2; htp.formClose; htp.bodyClose; htp.htmlClose; end; From Listing 10.7, you can see that as each row is retrieved from the DBA_HOST table, a variable called counter is incremented and then concatenated onto the name of the form field (in htp. formText). Listing 10.8 shows the HTML generated for this page. Listing 10.8 An HTML document with distinct repeating column names.<br />
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<HTML> <HEAD> <TITLE>s10</TITLE> <BR> <H1 ALIGN="C">DBA Display</H1> </HEAD> <BODY> <FORM ACTION="/ows-bin/owa/s10" METHOD="POST"> <INPUT TYPE="submit" NAME="s10ud" VALUE="Update DBA Information"> <BR> <BR> <H2>DBA name Responsibility phone e-mail office_hrs home phone : </H2> <BR> <INPUT TYPE="text" NAME="dba_name1" SIZE="10" MAXLENGTH="50" VALUE="burleson"> <INPUT TYPE="text" NAME="responsibility1" SIZE="10" MAXLENGTH="50" VALUE="PRIMARY"> <INPUT TYPE="text" NAME="dba_phone1" SIZE="10" MAXLENGTH="50" VALUE="777-7777"> <INPUT TYPE="text" NAME="dba_e_mail1" SIZE="30" MAXLENGTH="50" VALUE="l888888@ravingo"> <INPUT TYPE="text" NAME="dba_office_hrs1" SIZE="10" MAXLENGTH="50" VALUE="m-f 7-4"> <INPUT TYPE="text" NAME="home_phone_nbr1" SIZE="10" MAXLENGTH="50" VALUE="223-1836"> <BR> <BR> <INPUT TYPE="text" NAME="dba_name2" SIZE="10" MAXLENGTH="50" VALUE="papaj"> <INPUT TYPE="text" NAME="responsibility2" SIZE="10" MAXLENGTH="50" VALUE="BACKUP"> <INPUT TYPE="text" NAME="dba_phone2" SIZE="10" MAXLENGTH="50" VALUE="777-4444"> <INPUT TYPE="text" NAME="dba_e_mail2" SIZE="30" MAXLENGTH="50" VALUE="winner@roch"> <INPUT TYPE="text" NAME="dba_office_hrs2" SIZE="10" MAXLENGTH="50" VALUE="m-f 9-4"> <INPUT TYPE="text" NAME="home_phone_nbr2" SIZE="10" MAXLENGTH="50" VALUE="443-4446"> <BR> <BR> <INPUT TYPE="text" NAME="dba_name3" SIZE="10" MAXLENGTH="50" VALUE="rivera"> <INPUT TYPE="text" NAME="responsibility3" SIZE="10" MAXLENGTH="50" VALUE="OTHER"> <INPUT TYPE="text" NAME="dba_phone3" SIZE="10" MAXLENGTH="50" VALUE="551-5554"> <INPUT TYPE="text" NAME="dba_e_mail3" SIZE="30" MAXLENGTH="50" VALUE="5555555@cheo"> <INPUT TYPE="text" NAME="dba_office_hrs3" SIZE="10" MAXLENGTH="50" VALUE="m-f 5-4"> <INPUT TYPE="text" NAME="home_phone_nbr3" SIZE="10" MAXLENGTH="50" VALUE="555-5536"> <BR> <BR> </FORM> </BODY> </HTML> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/340-344.html (3 of 4)4/03/2005 6:16:10<br />
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Three rows were retrieved by cursor c2, and you can see a series of unique data names, dba_name1, dba_name2, and dba_name3. Now that uniquely defined form field names have been created, the information can be passed to ftp.formHidden, in exactly the same fashion as passing a single row. Then, each row will be updated by retrieving the column values using owa_parms.get.<br />
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Security And WebServer Forms For many database administrators, the terms open systems and security are oxymorons since it is often impossible to have open systems while maintaining adequate security. Maintaining security for a centralized system is difficult enough, and when faced with a network of networked databases, maintaining access and update security is a formidable challenge. In practice, security is an afterthought. In fact, its commonplace to see a lack of up-front planning for systemwide security, especially for distributed databases created as a result of external factors, such as corporate acquisitions. Oracle claims that WebServer is the first Web server to support full end-to-end security. By end-to-end, Oracle means that the WebServer maintains security at the database, server (via a firewall), and client levels, all while maintaining acceptable levels of performance. Let’s examine the security checks that take place when a PL/SQL request is made to the Oracle WebServer. Unlike an ordinary Web page where an HTML document is requested from a Unix flat file, Oracle provides far more security than the security permissions Unix maintains against HTML documents. With Oracle WebServer, the first level of authentication occurs when the PL/SQL agent connects to the Oracle server. In the WebServer configuration, only the predefined user may establish WebServer connections, thereby preventing anyone other than the PL/SQL agent from using the Web-Server mechanism to connect to an Oracle database. Once connected, the PL/SQL agent must identify itself to Oracle, using an Oracle username. The username is the key to Oracle’s security setup. The proper Oracle username grants<br />
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users the authority to load and execute stored procedures, enabling requested data to be gathered from the Oracle database. As a stored procedure is executed, the end user, using the proper password, gains the same access privileges as the owner of the stored procedure. Within Oracle, two methods are used to enforce security. The first (and most popular) method is the use of Oracle roles, whereby when a role is created, it is granted table and system privileges, and then is assigned to Oracle users. The second approach is the grant execute statement. With grant execute, privileges on a specific package or stored procedure are granted to users. When users execute the stored procedure, they automatically get the same privileges as the owner or creator of the stored procedure. It should be obvious that these two methods for managing Oracle security do not complement one another. The combined use of grant execute statements and rolebased security will eventually lead to a situation where it is impossible to determine the privileges of a user in an Oracle database. To understand how the “grant execute” method be implemented for WebServer, let’s take an in-depth look at Oracle security and how it can be applied to WebServer applications.<br />
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Oracle Security Oracle database security is applied with the SQL grant statement and removed with the revoke statement. While these two basic commands appear trivial, there are hundreds of different types of access privileges that can be granted and revoked. There are two categories of privileges that can be granted: table privileges (e.g., grant select on customer_table to Fred;), where a specific operation against a specific table is granted to a specific user, and system privileges (e.g., grant select any table to Fred;), whereby a range of privileges are granted to a specific user. In Oracle, access to tables is controlled with grant statements. Because grants are assigned for eac h SQL operation (select, update, insert, and delete) on each individual table, and because an application may consist of hundreds of tables, finding a way to group tables into functional categories can greatly simplify security administration. For example, some distributed Oracle databases have large replicated applications where each application may have hundreds of tables. For example, consider an income tax processing application that has a cloned database for each of the 50 states. When hundreds of tables are multiplied by 50 horizontal partitions, there are many thousands of distinct tables that must be granted to the end users. Clearly, maintaining grants on thousands of distinct tables would be a messy chore. The goal of WebServer security is to protect against the willful or accidental corruption of data, and to ensure that sensitive operations are controlled without being cumbersome for the DBAs or obtrusive to the end user. The solution to the maintenance of large numbers of tables is Oracle’s role-based security. As with all vendors, the Oracle implementation of role-based security is neither simple nor intuitive, and this section will discuss the major issues involved in establishing a role-based Oracle environment.<br />
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Oracle Privileges There are two classifications of grant commands: system privileges and object privileges. The difference is primarily one of scope; an object privilege is granted to a specific database object such as a customer table, while a system privilege applies to all instances of an object type.<br />
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System Privileges System privileges are the right to perform an action, or perform an action on all instances of a particular object type (e.g., grant select any table to jenny_burleson;). There are dozens of system privileges that can be used to regulate access to all functions within the database. System privileges are expressed in three parts: action, global (any), and object_type. Based on this taxonomy, system privileges are expressed with actions and the object types associated with actions: Action • • • • • • • • • •<br />
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create drop alter grant select audit (any) manage (tablespace) backup (table) force (transaction) become (user)<br />
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Object Type • • • • • • • • • • • • • • • •<br />
<br />
cluster procedure database database link privilege profile role session sequence snapshot system synonym table tablespace trigger user<br />
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Object Privileges Object privileges are the rights to perform an action on a specific, named object (e.g., grant update on cat.food to sarah_tytler;). Object privileges are usually expressed in the form action-object-objectname and are delineated in Table 10.1. Table 10.1Object privileges. Object Privilege<br />
<br />
Tables<br />
<br />
Views<br />
<br />
Sequences<br />
<br />
Snapshots<br />
<br />
all<br />
<br />
x<br />
<br />
x<br />
<br />
x<br />
<br />
x<br />
<br />
alter<br />
<br />
x<br />
<br />
delete<br />
<br />
x<br />
<br />
index<br />
<br />
x<br />
<br />
insert<br />
<br />
x<br />
<br />
references<br />
<br />
x<br />
<br />
select<br />
<br />
x<br />
<br />
x<br />
<br />
update<br />
<br />
x<br />
<br />
x<br />
<br />
x x x x<br />
<br />
You can combine certain object privileges with objects. Therefore, the following object privileges are valid examples: grant all on papaj_table to andy_burleson; grant insert on my_view to patty_tytler;<br />
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Functions, Stored Procedures, And Packages One of the most important features for WebServer security is the ability to enforce access to a table by using functions, stored procedures, and packages. A function is a code snippet that can contain SQL that accepts input variables and returns values to the caller of the function. A stored procedure is a piece of code that has embedded SQL commands within its body. A package is a collection of Oracle stored procedures and/or Oracle functions that logically bundles the stored procedures together into a single unit. For example, the following Oracle package, called human_resources, contains the functions and stored procedures that are required to perform HR tasks: create package body human_resources AS; procedure hire_employee begin ... end; function give_raise begin ... end; procedure manage_adjunct begin ... end; The confounding problem with procedures and packages is that their security is managed in an entirely different fashion from other grant statements. When a WebServer developer role is given execute privileges on a package, the user executing the package will be operating under the security domain of the owner of the procedure, and not their own defined security domain. In other words, a user who does not have privileges to update employee rows can get this privilege by being authorized to execute a procedure that updates employees. From the DBA’s perspective, a database security audit would not reveal this update capability. The Oracle documentation describes the operation of stored procedure security and how it differs from role-based security. The application developer’s guide states that “the owner (of a stored procedure) cannot have obtained required privileges through roles.” It also follows that someone cannot grant execute on a stored procedure to a role. execute must be explicitly granted to a user—bypassing all roles. While this may sound like a bug, Oracle calls it a “design issue.” However, there is an enhancement request asking for this process to be changed (Oracle enhancement request #168358). This issue is also covered in Oracle bulletin #105025.435 Role Restrictions, with an explanation of why this restrictio1n exists. The same security principle applies to using Oracle triggers. For example, a user cannot create a trigger based on privileges that they received by being granted a role. Following the same rule, a user cannot create an Oracle stored procedure based on privileges that they received through being granted a role. The exclusive grant to the users works because the grant is not coming from a role.<br />
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Assigning Privileges As mentioned earlier in this chapter, privileges are granted or revoked at the individual user level. Because all privileges and users are specified at the most atomic level, a database with 10 tables and 100 users would require 4,000 specific grant statements. Fortunately, Oracle SQL provides a method for categorizing privileges and users, making security more manageable. Object privileges can be combined into a single grant statement. For example, when a table is created, access to the table is limited to the creator of the table. If user CAT creates a table called FOOD, then access to the table could be granted to all users with the statement: GRANT SELECT, INSERT, UPDATE, DELETE on CAT.FOOD to USER1, USER2;<br />
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Cascading Grant Privileges One confounding feature of Oracle SQL is the cascading ability of grant privileges. If USER1 has been given a privilege with the grant option, that user now has the ability to grant their privileges to any other user. For example, if the DBA issues the statement grant all on MY_TABLE to sarah_tytler with grant option, sarah_tytler may now distribute this privilege to andy_burleson by stating grant all on MY_TABLE to andy_burleson with grant option. To further confound matters, andy_burleson may now, in turn, give this privilege to other users, and so on, ad infinitum. Fortunately, the grant option clause in Oracle does not work with roles. Therefore, the following statement would not be permitted in Oracle: grant MY_ROLE to USER1 with grant option;<br />
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Cascading revokes only apply to non-DDL system privileges and object privileges. For example, consider the following sequence of commands: DBA: USER1: USER1: DBA:<br />
<br />
grant create table to USER1 with admin option; create table user1.my_table; grant create table to USER2; revoke create table from USER1;<br />
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In this scenario, USER2 continues to have create table privileges even though the create table privilege has been revoked from the user who granted the privilege to USER2. The moral is: Don’t use the admin option. In all other cases (except system DDL privileges), the initial revoke will cascade to all who have been granted the privilege. A good example is a table owner, who grants select privileges to USER1 with grant option, and then USER1 grants select to all of his friends. When the table owner revokes the select privilege from USER1, all users who received their grant from USER1 will also lose their privileges. A more extreme example would be when the DBA allows anyone to select from a table (grant select any table to public), and then revokes the privilege (revoke select any table from public). Any select references to any tables in the entire database will fail, unless other object privileges have been used to grant access. grant Statements When using grant statements, there is a method to negate all security for a specific object. Security can be explicitly turned off for an object by using public as the receiver of the grant. For example, to turn off all security for MY_TABLE, you could enter: grant all on MY_TABLE to public; Security is now effectively turned off for MY_TABLE, and restrictions may not be added with the revoke command. For example, if USER1 and USER2 are not allowed to delete rows from MY_TABLE, you could not enter revoke delete on MY_TABLE to USER1. The public parameter cannot be negated with revoke statements. Roles In Oracle, roles may be assigned to sessions, as well as individual users. For example, assume that you want a user to have the role of customer_clerk, but only when the user is within the control of the customer service application. When the user invokes the main menu for the customer service application, the application could disable all previous roles for this user and force them into the customer_service role as follows: set role none; set role customer_service; Note that the set role command cannot authorize users for roles that they have not been granted privileges to use. Therefore, you must first grant the customer_service role to each end user. Row-Level And Column-Level Security For some WebServer applications, you may need to restrict access to certain columns within a table, or even to certain rows within a table. By using roles with relational views, it is possible to restrict select access to individual rows and columns within an Oracle table. For example, assume that a PERSON table contains confidential columns, such as salary. Also assume that this table contains a type column with the values exempt, non_exempt, and manager. Let’s say you want your end users to have access to the PERSON table, but you wish to restrict access to the salary column and the manager row. A relational view could be created to isolate the allowed columns and rows, as follows:<br />
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create view USER_VIEW as select name, address, phone, history, comments, type from person where type <> "manager" ; You could now grant access to this view to any Oracle user; grant select on USER_VIEW to public; Oracle also allows grant statements to specify individual table columns, but column-level security can only be used with update, insert, and references grants. Columns can be specified in the grant statement with the columns enclosed in parentheses, as follows: grant update (salary, date_of_birth) on EMPLOYEE_TABLE to MARIA_HESS; If you wish to change the grant to specify only the salary column, Oracle requires that all privileges be revoked, and the individual columns readded. For example, the following code would revoke update privileges for the salary column: revoke update on EMPLOYEE from MARIA_HESS; grant update (date_of_birth) on EMPLOYEE_TABLE to MARIA_HESS;<br />
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Table Synonyms In Oracle, synonyms are used to assign nicknames to tables. Synonyms are most commonly used within Oracle to avoid having to qualify each table name with the name of the user who created the table (e.g., create public synonym customer for MARIA_HESS.customer;). In a distributed Oracle environment, synonyms are often granted to tables in order to avoid the use of the location qualifier in the table name. For example, the Oracle statement create public synonym EMPLOYEE for emp.employee@london; requires the developer to know that the EMPLOYEE table is located in London (where @london is the TNS service name for Oracle SQL*Net). Synonyms are also commonly used to hide the table owner name so that the SQL does not have to specify the table owner. For example: create public synonym CUSTOMER for CUSTOWNER.customer@albuquerque; allows the table to be referred to as CUSTOMER without any reference to the table owner of the TNS location of the table. A grant to a table automatically allows access to a table by its synonym, and also allows grants to be specified for a table according to the synonym. In the following example, the user MYUSER is granted access to the synonym emp for access to the table CAT.EMP. This grant will remain in effect even if the synonym emp is dropped: create synonym emp for cat.emp; grant select on emp to MYUSER; drop synonym emp; Session-Level Security<br />
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Session-level security can be enforced within WebServer, as well as within the Oracle database. For example, a user may have update authority when accessing the customer data through the WebServer application, but the authority should be rescinded if the user attempts to update customers within SQL*Plus. To allow this, Oracle provides the PRODUCT_ROLE_MANAGER_PROFILE table to enforce tool-level security, and the user may be disabled from updating in SQL*Plus by making an entry into this table. For example, to disable updates for user FLORENCE_FOOS, the DBA could state: insert into PRODUCT_ROLE_MANAGER_PROFILE (product, userid, attribute, char_value) values ("SQL*Plus", "FLORENCE_FOOS", "update", "disabled"); The user named FLORENCE_FOOS could still perform updates within the application, but would be prohibited from updating while in the SQL*Plus tool. At this time, the following values for the attribute column are being used: • • • • • • • •<br />
<br />
begin copy declare delete edit host insert update<br />
<br />
In Oracle, you can disable unwanted commands for end users by using a wildcard in the attribute column of the PRODUCT_PROFILE table. For example, to disable the delete command for all users of SQL*Plus, you could enter: insert into PRODUCT_ROLE_MANAGER_PROFILE (product, userid, attribute, char_value) values ("SQL*Plus", "%", "delete", "disabled"); Unfortunately, while this is great for excluding all users, you cannot alter the tables to allow the DBA staff to have delete authority. The only acceptable value for the char_value column is disabled. Grants And Distributed Oracle Databases When an Oracle connection is made to a remote database, the security in the remote database will be applied to the transaction, regardless of the security on the WebServer database. In other words, the security is regulated at the remote destination, and the privileges at the WebServer database are irrelevant. For example, assume that USER1 has grant select any table to USER1; on database1 privileges. If USER1 attaches to a remote database, say database2, his grant has no authority on tables that reside in database2. For distributed Oracle queries, the user must have proper privileges on both of the databases involved in the update. For example, a user in London may join two tables from New York and California, as follows: create synonym ny_customers for customer@ny; create synonym ca_customers for customer@ca; select * from ny_customers, ca_customers;<br />
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At the time of the select, the user must have select privileges against both of the customer tables or the entire transaction will fail. Implementing Role-Based Security As previously discussed, the recommended security option for WebServer is to assign roles to key developers who create the PL/SQL stored procedures for WebServer. At the highest level, role implementation for WebServer applications entails the following steps: 1. 2. 3. 4. 5. 6. 7. 8.<br />
<br />
Create empty roles/passwords. Identify privileges associated with the roles. Assign table privileges to the roles. Identify the key developers who will belong to each role. Grant these roles to the key developers who will create the Oracle stored procedures. Revoke all existing table-level object privileges and grants to public. Have the key developers create the WebServer stored procedures. Grant execute privileges for these stored procedures to the end-user community.<br />
<br />
For existing systems, a new role-based security plan will replace all table-level grants with rolelevel grants. All roles will be defined at the table-owner level (e.g., SALES, ADJUNCT), and these roles will be combined so that all existing security is duplicated. The existing table-level security will be cleaned up and replaced with roles. This approach will take every existing application one at a time and perform the following steps. (We’ll assume that the existing security is adequate for the protection of confidential information, and that any holes in the SQL security are taken care of within the application code.) 1. Investigate the current security mechanism. Look at the grants for all of the tables, cross-referencing the grants with the users. For tables with grants to public, all systems users will be granted access. Check for and remove all grant options and with admin options. Now, use a script to check the existing grant security for each database. 2. Create a role (or roles) to match each functional category of the WebServer application. 3. Grant access to the roles for each user, based on the table-level grants from Step 1. A script exists (role.sql) to create the SQL syntax for converting table-based grants to rolebased security. 4. Drop all direct grants to tables, with the exception of the role grants. Notify the end users, and carefully watch for security problems.<br />
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Creating Key Developer Roles A few simple guidelines should be followed when determining the proper roles to assign to the WebServer developers who will create the stored procedures. Remember, roles will be used by key developers when they create PL/SQL stored procedures, and the privileges maintained by the key developers should be the same as those required to execute the stored procedure. In addition, using Oracle views may simplify security maintenance. In Oracle, a view is a “logical” table that is comprised of numerous tables. For example, consider the following view definition: Create view order_form as select customer_name, order_number, order_date, item_number, quantity_ordered, item_description, item_cost from customer, order, line_item, item where customer.customer_name = order.customer_name and order.order_number = line_item.order_number and line_item.item_number = item.item_number; Now that this view has been created, it can be referenced as if it were a single, logical table. For example, the following query will hide all of the complexity involved in the Oracle database retrieval:<br />
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select * from order_form where order_number = 123; In summary, the guidelines for effective role development include the following: • Avoid fine-grained security (row-level and column-level security). • Never allow the grant option or with admin option. • Encourage the use of procedures and packages. • Encourage the use of views because they can encapsulate SQL into logical pieces, simplifying security administration. Because SQL security for applications is currently controlled at the table level, and an application may consist of hundreds of tables, finding a way to group tables into functional categories can greatly simplify administration. Functional security can be implemented using either role-based or procedure-based categorization. For existing systems, role-based security can be implemented without disturbing existing applications. With WebServer-based development, roles are created for each developer, but be aware that special, readonly roles may be created for linking between remote Oracle databases.<br />
<br />
NOTE: When a view spans table-owners, all tables from a foreign owner (i.e., other than the owner of the view), must be granted to the view-owner with grant option. Then, the view-owner can grant the view to roles, because he is now allowed to grant access for the specific foreign-owner tables.<br />
<br />
Each key developer role should consist of the table privileges required to perform application development in the particular area. For example, a developer can not have drop any table privileges, because they would have the ability to drop tables belonging to other applications. Therefore, the developer roles should be tied to the role of the table-owner for their application. For example, the table-owner adjunct would own full privileges on all objects created by adjunct, but could not drop tables belonging to sales. To create a developer role for adjunct, the following SQL could be issued to allow full access to any objects within the specified schema with: grant schema_privilege on schema to schema_developer; Within their schema, developers require full system privileges on schema objects, including clusters, tables, indexes, sequences, synonyms, tablespaces, triggers, and views. In addition, system privileges must be assigned to the developers. System privileges include unlimited tablespace, connect, and resource. A sample grant statement might appear as follows: grant create table, create index on CUSTOMER_TABLE to CUSTOMER_DEVELOPER; Each area within the WebServer application would get its own role assignment, which would encompass all of the valid authorities needed by the end users. These roles would be similar to the authority of the tableowner, but, instead of granting adjunct to public, the tables would be granted to the role associated with the application. Note that roles, just like users, may be assigned passwords. For example: create role ADJUNCT_ROLE_MANAGER create role ADJUNCT_ROLE_SELECT<br />
<br />
identified by xxx; identified by xxx;<br />
<br />
grant all on ADJUNCT.table1, ADJUNCT.table2 to ADJUNCT_ROLE_MANAGER; grant select on ADJUNCT.table1, ADJUNCT.table2 to ADJUNCT_ROLE_SELECT; grant ADJUNCT_ROLE_MANAGER to OPS$username; For WebServer applications that access remote databases, select-only versions of the role could be<br />
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associated with the user ID that associates with the link. If a user requires access to more than one tableowner, the roles could be combined, as follows: create user ADJDB_link identified by xxx; grant ADJUNCT_ROLE_SELECT, S125_ROLE_SELECT to ADJDB_LINK; At this point, you could specify ADJDB_LINK on any target system that requires a database link: create public database link ADJDB_LINK connect to ADJDB_LINK identified by xxxx using 't:pdc:adjdb';<br />
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An Implementation Plan For WebServer Security Once the appropriate roles have been identified and the privileges have been determined, a plan must be devised to replace existing table-level security. Replacing table-level security must be done unobtrusively. Ideally, end users and developers should not be aware that a change has occurred. Replacing table-based security with role-based security includes the following steps: 1. Make changes to the database one step at a time. 2. Review the existing security for each database. Identify all table grants. The following query will display all Oracle tables and table-level privileges against each Oracle table: select distinct table_name, privilege from dba_tab_privs; 3. Assign all table-level grants to a new role. The following statement creates two roles and then assigns the new roles to Oracle users: create role SCHEMA_ROLE_MANAGER identified by xxx; create role SCHEMA_ROLE_SELECT identified by xxx; grant all on table1, table2 to SCHEMA_ROLE_MANAGER; grant select on table1, table2 to SCHEMA_ROLE_SELECT; 4. Interrogate all end users to get their existing grants (if any). The following code lists all Oracle users whose user ID begins with ‘OPS$’ who have been granted tablelevel privileges:<br />
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select * from dba_tab_privs where grantee like 'OPS$'; 5. Create and assign roles to all appropriate users. The following code creates a role and assigns the role to a user: create role schema_ROLE_MANAGER identified by xxx; grant xxx on table1, table2, to schema_ROLE_MANAGER; 6. Revoke existing grants (except the role) from users. The following code revokes specific table-level privileges from a named user: revoke select, update on table1, table2 from ops$username; 7. Wait one week. If there are no reported problems, revoke all grants to tables (except the role). The following code revokes specific grants from public access: revoke select, update on table1, table2 from public; 8. Locate all other databases that access the database, and alter the links to specify the read-only user ID instead of a table-owner ID. The following code ensures that a database link uses a specific user ID when connecting to the remote database: alter database link SCHEMA connect to SCHEMA_ROLE_SELECT identified by xxx; Role Allocation Strategy For WebServer For WebServer applications that have successive degrees of refinement, you may want to consider organizing roles in a hierarchy—assigning developers roles according to their individual needs. For example, some key developers might write read-only queries against a set of Oracle tables, while other developers might create the stored procedures that actually update this set of tables. New roles can be created from existing roles, system privileges, object privileges, or any combination therein, as shown in Figure 10.8.<br />
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Figure 10.8 A sample hierarchy of Oracle roles. Data-Specific Vs. Application-Specific Security Application-specific security can give much tighter control over security than data-specific security. The DBA can authorize application owners to have the proper privileges to perform their functions, without granting end users any explicit grants against the database. Instead, end users are granted execute on the procedure, and the only way end users will be able to access the data is through the procedure (e.g., grant execute on human_resources to JONES;). For specific applications, the user ID that serves as the table owner (e.g., custowner. customer) can be used as the creator of the procedures. Table owners automatically receive file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/359-361.html (2 of 3)4/03/2005 6:16:13<br />
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all authority against the tables they create, so no DBA intervention is necessary. Because the procedures govern what the end user can and cannot perform, the only administration required would be to bundle the procedures into a package and grant execute privileges to the appropriate end users. There is no need to create huge grant scripts for each and every end user, and there is no possibility of end users doing an end-run and accessing the tables from within other packages. Of course, this would require coordination with the application programmers, so that all SQL is encapsulated into functions and procedures. Any SQL inserted directly into the application code will fail at runtime. The PROCESS of consciously encapsulating code into functions and procedures is beneficial for a number of reasons, including: • Reusability—Functions and procedures can be written independently and reused in a variety of ways within the application. • Isolation—Each procedure can be tested as a finite unit, so application changes are simplified, and the programmers can be assured that unintended side effects are not introduced into their environment. • Security—Security is maintained directly by the procedures and functions, and the data is protected from being altered from anyone outside the domain of the procedures.<br />
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Automatic Conversion To Role-Based Security An SQL script can create role-based security privileges, as shown in Listing 10.9. Once an existing schema table owner has been located, the following script can be used to generate all of the SQL. Listing 10.9 A script to create a role with all privileges of a schema table owner. [oracle]: more role.sql set heading off; set pause off; set echo off; set termout off; set linesize 75; set showmode off; set feedback off; set newpage 1; set verify off; set pagesize 9999; spool /tmp/&1.role.sql select select select select select<br />
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'— Create the two new roles. ' from dual; 'create role &1._role_manager identified by xxx;' from dual; 'create role &1._role_ROLE_SELECT identified by xxx;' from dual; '— If there were select privileges, ' from dual; '— grant these selects to _role_ROLE_SELECT. ' from dual;<br />
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select distinct 'grant SELECT', ' on ', substr(table_name,1,20), ' to ', '&1._role_ROLE_SELECT;' from dba_tab_privs where<br />
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owner = '&1' and privilege = 'SELECT'; select '— If there were non-select privileges, ' from dual; select '— grant these privileges to _role_ROLE_SELECT. ' from dual; select distinct 'grant ', substr(privilege,1,12), ' on ', substr(table_name,1,20), ' to ', '&#amp;1._role_manager;' from dba_tab_privs where owner = '&1' and privilege <> 'SELECT'; select '— If the users were granted to specific privileges, ' from dual; select '— grant these privileges to the new role. ' from dual; select distinct 'grant ', substr(privilege,1,12), ' on ', substr(table_name,1,20), ' to ', '&1._role_manager;' from dba_tab_privs where owner = '&1' and grantee <> 'PUBLIC'; select '— If the privilege was granted to PUBLIC, ' select '— grant the privilege to all system users.'<br />
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from dual; from dual;<br />
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select distinct 'grant ', '&1._role_manager', ' to ', substr(username,1,12), ';' from dba_ROLE_MANAGERs; select '— If the privilege was granted to specific users, ' from dual; select '— grant the role to those users ' from dual; select distinct 'grant ', '&1._role_manager', ' to ', substr(grantee,1,12), ';' from dba_tab_privs where owner = '&1' and grantee <> 'PUBLIC'; select '— Revoke all table-level privileges for the owner. ' from dual; select distinct 'revoke ', substr(privilege,1,12), ' on ', substr(table_name,1,20), ' from ', substr(grantee,1,12), ';' from dba_tab_privs where owner = '&1'; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/361-365.html (2 of 3)4/03/2005 6:16:14<br />
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spool off; set termout on; prompt Roles for &1 has been written to /tmp/&1.role.sql Auditing Security In A Distributed Oracle Environment There is a general philosophy regarding WebServer security and Oracle: Create a framework to manage security in a simple fashion. To achieve simplicity, the following guidelines are strongly recommended: • • • • •<br />
<br />
Prohibit the use of grant…with admin option. Prohibit the use of grant…with grant option. Prohibit any object grants to public. Require the use of role-based security. Insist upon the complete use of function-procedure-package security.<br />
<br />
To audit a distributed Oracle WebServer application, each remote database must be checked for unusual grants and situations where a user has received privileges (either system or object privileges) from an unauthorized source. As each database is visited, an audit file will be produced for the DBA to review. The database dictionary can be interrogated to show the following security breaches: • Any system privileges granted with admin option (DBA_SYS_PRIVS table)—Remember, this scenario can be a danger because anyone who receives a system privilege with admin option may grant his privileges to others. • Any non-DBA roles granted with admin option (ROLE_SYS_PRIVS table)—All system privileges and roles can be granted with admin option, and it’s important to ensure that roles aren’t floating around that could be granted to others. • End users with table privileges grantable to others (DBA_TAB_PRIVS table)—End users who have grant option object privileges. Just as system privileges and roles can be granted with admin option, object privileges can be granted with grant option. It’s important that nobody (except table owners) may grant table privileges to others. • End users who have received a grantable privilege (ALL_TAB _PRIVS_RECD table)—Anyone who receives a system or object privilege from anyone except SYS will be reported in this list. The person who granted the privilege will appear in the grantor column, and it should correspond to a grantee name in DBA_TAB_PRIVS and/or DBA_SYS_PRIVS. If the offending grantee has his admin or grant option revoked (i.e., revoke privilege from grantee cascade constraints), the revoke should cascade into ALL_TAB_PRIVS_RECD, and these entries will disappear. • End users with roles (other than resource and connect) (DBA_ROLE_PRIVS table)—This table lists any roles other than resource and connect for all users except OPS$ORACLE, SYS, SYSTEM, and DBA. This table will show anyone who has wrongly acquired DBA privileges. • End users with system privileges (DBA_SYS_PRIVS table)—This table shows all users who have system privileges. In some cases, it’s okay for a user to have unlimited tablespace, but other privileges such as drop table should be carefully monitored.<br />
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In any Oracle environment, it’s a good idea to check for unusual security conditions on a regular basis. Listing 10.10 shows a script used to check for unusual Oracle security. Listing 10.10 A script to check for unusual Oracle security. *************************************************** prompt Searching &1 for system privileges granted WITH ADMIN OPTION... select * from dba_sys_privs where admin_option = 'YES' and grantee not in ('DBA','SYSTEM','SYS','OPS$ORACLE'); *************************************************** prompt Searching &1 for non-dba roles granted WITH ADMIN OPTION... select * from role_sys_privs where role <> 'DBA' and admin_option = 'YES'; *************************************************** prompt Searching &1 for table privileges that are grant-able to others... select substr(grantee,1,12), substr(table_name,1,20), substr(privilege,1,10), substr(grantable,1,3) from dba_tab_privs where grantable = 'YES' and owner not in ('SYS','SYSTEM','GL','APPLSYS','BOM','ENG', 'PO','AP','PER','WIP','LOGGER');<br />
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*************************************************** prompt Searching &1 for users who have received a grantable privilege... select * from all_tab_privs_recd Where grantable = 'YES' and owner not in ('SYS','SYSTEM'); *************************************************** prompt Searching &1 for folks with roles (other than resource/connect)... select * from dba_role_privs where granted_role not in ('RESOURCE','CONNECT') and grantee not in ('OPS$ORACLE','OPS$ADMOPR','DBA','SYS','SYSTEM'); *************************************************** prompt Searching &1 for folks with system privileges... select * from dba_sys_privs where privilege <> 'UNLIMITED TABLESPACE' and grantee not in ('COMMON','OPS$ORACLE','RESOURCE','CONNECT','OPS$TPSOPR', 'IMP_FULL_DATABASE','DBA','SYS','SYSTEM','OPS$ADMOPR', 'EXP_FULL_DATABASE'); *************************************************** Auditing Oracle Role-Based Security Once a set of roles has been established and all grants to public have been removed, an audit script can be used to ensure that there are no holes within the role framework. As each database is visited, an audit file will be produced for the DBA to review. As you can see in Listing 10.10, the Oracle dictionary can be interrogated to show all security breaches. Another method of security auditing is to use a script to show the privileges contained within a role, as shown in Listing 10.11. The script in Listing 10.11 accepts a role name and produces a report that shows all of the role’s users and privileges. Be wary when you run this script, though, because it can be a huge report, with many thousands of lines of output. Listing 10.11 role.sql <role_name> showing all role users and privileges. set set set set set<br />
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pause off; echo off; termout on; linesize 80; pagesize 999;<br />
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column c1 heading "Role"; column c2 format a40 heading "Table Name"; column c3 heading "Priv."; break on c1 skip 0 on c2 skip 0 on c3 skip 0 ttitle "Role &&1 in Database dbname"; select substr(granted_role,1,29) c1 from sys.role_role_privs where role = (upper('&&1')) ; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/365-368.html (2 of 3)4/03/2005 6:16:15<br />
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select substr(role,1,30) c1, ltrim(rtrim(owner))||'.'||substr(table_name,1,29) c2, substr(privilege,1,6) c3 from sys.role_tab_privs where role = (upper('&&1')) order by 1,2,3; column c1 heading "Role"; column c2 heading "Grantee"; ttitle "Users with &&1 role"; select substr(granted_role,1,10) c1, substr(grantee,1,20) c2 from dba_role_privs where granted_role = (upper('&&1')) order by 1,2; Here are the results from Listing 10.11: SQL > @role dba Fri Mar<br />
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page<br />
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1<br />
<br />
Role dba in Database dbname Role ————— EXP_FULL_DATABASE IMP_FULL_DATABASE Users with dba role Role Grantee ————————————————————————— DBA ORADBA SYS<br />
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Listing 10.12 is another SQL script useful for showing role information. Listing 10.12 shows all the roles within Oracle, all system and table privileges that comprise each role, and finally, all users who have been granted each role. Again, be forewarned that this can be a very large report if the Oracle instance has many roles. Listing 10.12 An SQL report giving complete role information. rem roles.sql - Shows all roles with database and all users (huge report) set set set set<br />
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pause off; echo off; linesize 80; pagesize 60;<br />
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column c1 heading "Role"; column c2 format a40 heading "Table Name"; column c3 heading "Priv."; break on c1 skip 0 on c2 skip 0 ttitle "Roles in Database dbname"; select substr(role,1,30) c1, substr(granted_role,1,30) from sys.role_role_privs; ttitle "Roles in Database dbname"; select substr(role,1,30) c1, ltrim(rtrim(owner))||'.'||substr(table_name,1,30) c2, substr(privilege,1,6) c3 from sys.role_tab_privs where owner not in ('SYS','SYSTEM') order by 1,2,3; column c1 heading "Role"; column c2 heading "Grantee";<br />
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ttitle "Roles Granted to Users in Database dbname"; select substr(granted_role,1,30) c1, substr(grantee,1,20) c2 from dba_role_privs where granted_role not in ('DBA','RESOURCE','CONNECT','SYS','SYSTEM', 'EXP_FULL_DATABASE','IMP_FULL_DATABASE','MONITORER') order by 1,2; Here is the output from Listing 10.12: SQL> @roles Fri Mar 8<br />
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page 1 Roles in Database<br />
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Role ————— DBA<br />
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SUBSTR(GRANTED_ROLE,1,30) ——————————————— EXP_FULL_DATABASE IMP_FULL_DATABASE<br />
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2 rows selected. Fri Mar<br />
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8<br />
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page 1 Roles in Database<br />
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Role —————<br />
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Table Name Priv. ————————————————————————————————————————————————— —————<br />
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ORORACLEUSR<br />
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ORACLE.CUSTOMER<br />
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ORACLE.CATALOG<br />
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ORACLE.CHOICE<br />
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ORACLE.DATES<br />
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ORACLE.MASTER<br />
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ORACLE.CUSTOMER_TYPE Fri Mar<br />
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Role —————<br />
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8<br />
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DELETE INSERT SELECT UPDATE DELETE INSERT SELECT UPDATE DELETE INSERT SELECT UPDATE DELETE INSERT SELECT UPDATE DELETE INSERT SELECT UPDATE SELECT<br />
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page 1 Roles Granted to Users in Database dbname Grantee —————————————————————————————————————————————————<br />
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ORACLEDEV bob_papaj mark_reulbach sarah_papaj eddie_papaj file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch10/368-372.html (2 of 3)4/03/2005 6:16:15<br />
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bryan_papaj rebecca_papaj stephanie_papaj debbie_schumacher ORACLEUSR EMANS GENERAL KRAMER Propagating Security Privileges To Many Distributed Oracle Databases For very large WebServer applications with more than 50 remote databases, the propagation of database code and audits can become a major headache. The script shown in Listing 10.13 can be used in a Unix environment to read a list of remote processors, access each one, find all databases on each processor, and perform the same function on each database. The script in Listing 10.13 has been used to run SQL security audits on more than 70 distributed databases, all from a single task on the master processor. Listing 10.13 Korn shell script used to visit each Oracle database on a host. for HOST1 in 'cat hostlist| cut -d":" -f1' do echo " " echo "===============" echo "HOST= $HOST1" echo "===============" # Now, get all of the database names on each box... for DB in 'remsh $HOST1 -n "cat /etc/oratab | grep /usr/oracle:Y|cut -d":" -f1"' do echo " " echo " ———————" echo " DB= $DB" echo " ———————" #Now, we log into the database TWO_TASK=t:$HOST1:$DB export TWO_TASK DB su oracle -c "sqlplus /<<! spool $DB.audit start audit $DB exit; !" done done The increasing sophistication of software tools used to manage role-based security is making significant inroads, but there is still a need for DBA staff members to control data access and to customize unobtrusive security frameworks. As end users continue to demand more and more seamless access to distributed information, increasingly sophisticated role-based security frameworks will have to be devised.<br />
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The Ten Commandments For Oracle Security In order to get started with Oracle security, the following guidelines can be followed. While these are very general security guidelines, they can be used as a starting point for the development of a comprehensive set of Oracle WebServer security access rules: 1. The DBA is ultimately responsible for Oracle security. Hence, the DBA is responsible for the creation and maintenance of all Oracle roles. 2. All privileges (both object privileges and system privileges) will be placed into roles. Privileges will never be directly granted to end users. ** 3. All roles will be protected with a password, and the role password will be embedded into the application so the end users will never know the passwords for the roles that they have been granted. (This is to alleviate the problem of end users bypassing an application and issuing updates within MS-Query or SQL*Plus.) 4. Thou shalt never grant any system privileges with ADMIN OPTION, nor any table privileges with GRANT OPTION. 5. Only one end user shall be the role administrator (RA). The RA will be responsible for granting the roles to the end users, and will be granted ADMIN OPTION for each role that they administer. A special role called “RA” shall be created with the CREATE ANY USER privilege and granted to the RA. 6. The RA will have neither DROP ANY USER nor ALTER ANY USER privileges. The DBA will be responsible for dropping end-user IDs, and each end user will be responsible for maintaining their own Oracle passwords, either via MS-Query, SQL*Plus, or through an application screen. 7. Only the SYS and SYSTEM users shall be granted the DBA role.<br />
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8. There will be only three roles for IS personnel: CONNECT, RESOURCE, and DBA. These roles will contain the same privileges within all Oracle databases. 9. Tables may be granted to PUBLIC whenever security is not an issue. 10. Oracle security shall be audited twice each year to ensure that these rules are followed. ** The exception to number two is UNLIMITED TABLESPACE, which cannot be assigned to a role (ORA-01931: cannot grant UNLIMITED TABLESPACE to a role).<br />
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Summary This chapter covers the basic WebServer form functions. After reviewing this chapter, you should be able to create WebServer pages that access and update Oracle databases and manage WebServer security. Next, the following chapters will take a look at managing entire WebServer-based applications, including addressing issues such as concurrency, lock management, performance, tuning, and distributed WebServer applications.<br />
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CHAPTER 11 WebServer Navigation And Concurrency Management Ever since the introduction of online systems, developers have had to face the challenges of managing transfers between online screens. When database technology was introduced, the database interscreen transfer became even more challenging, and developers had to maintain currencies. These currencies enabled end users to return to a database at the same point where they left off. Today, we are using Web pages as the vehicle for screen display, but the principles that applied to BMS screens with CICS in the 1960s still apply to interscreen management of WebServer pages.<br />
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Interscreen Transfer For Oracle databases, the concept of database currency means saving all of the rowids for all current Oracle rows on the Web page. Traditionally, there have been three ways that a developer could manage a transfer between the current screen and a destination screen: • Invoke—An invoke retains database currencies from the current screen and makes them available to the destination screen. In other words, a current Oracle file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch11/375-378.html (1 of 3)4/03/2005 6:16:16<br />
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row will be available to later screens for processing. For example, say screen sh100 displays customer information, screen sh200 displays order information, and screen sh300 displays order detail information. As the end user invokes the lowest level sh300 screen, the current Oracle CUSTOMER table rowid and ORDER table rowid are known to the sh300 screen, and these values can be used in SQL as needed. • Transfer—A transfer allows for movement between screens without any maintenance of database currencies. For example, if you transferred from screen sh100 to screen sh200, then transferred back to screen sh100, the database information about your previous visit to screen sh100 would not be retained. • Link—A link is a one-way transfer to a destination screen with an immediate return to the current screen. Link screens are generally used to display exception information (error screens) or show detail (detail screens), and they immediately return to the invoking screen after displaying the message. In general, a link can be thought of as a subroutine call, such as a call to a calculation function. For WebServer, the decision of whether to invoke, link, or transfer is the same as with any other type of Oracle application. The difference with WebServer lies in the way screens are processed by the Web pages. In WebServer, there are several ways to move to a new screen: • htp.anchor—Embeds a URL behind a text string (or image) and transfers control to the Web page specified by the URL. This is commonly referred to as a hyperlink. • htp.formSubmit—Creates a button on a Web page that, when clicked, transfers to the screen name specified. • htp.formImage—Creates an online picture that can be clicked to transfer to another Web page.<br />
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Note: There are two ways to specify the destination screen name with the htp. formSubmit procedure. One method is to code the screen name (which is a stored_procedure name) directly in the formSubmit statement, or you may use htp.formHidden to send the contents of a field along with the submitted form.<br />
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Interform Communication Just like any other database application, WebServer applications will have an overall structure. There will generally be some form of main menu, with sublevels of screens that branch from the menus. The design of the menu hierarchy is the starting point for most online applications, and this function has not changed with Oracle WebServer (see Figure 11.1).<br />
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Figure 11.1 Example of a menu model for a WebServer application. At this point, most of the basic rules of online application development apply, and the fact that the output is displayed in a Web page is only an additional consideration. However, there is one interesting feature worth noting. In most application designs, each submenu has an exit function, which will return control to a higher menu. When using WebServer, these exit functions are not necessary because it is a simple matter for users to select the Back button on their Web browsers to return to a Web page. In a traditional application, transferring between screens implied that the application would need to keep placeholders, or row currencies, so that the application could remember where you were before you left. In WebServer, the architecture dictates that each Oracle transaction terminates after executing the PL/SQL stored procedure. Consequently, we must develop a method for retaining the database currencies—and remember, SQL statements that issue locks are not allowed within WebServer. For example, the PL/SQL within WebServer stored procedures may not issue the statement select customer_name from customer for update of customer.<br />
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Database Locking And Concurrency Management For any database that has many end users updating tables, a method must be used to ensure that each update transaction does not overlay the updates of the other end users. This method is generally called concurrency management, and it is a very important topic for WebServer applications. While most commercial database products provide for locking and concurrency control, there are new issues when using a distributed WebServer database. These problems are especially prevalent when a single Web page updates several databases. In addition to the technical issues, the popularity of Webbased interfaces has also changed how concurrency is handled. Many Web-based Oracle systems disable their database locking and rely on procedural tricks to maintain data integrity. The following sections of this chapter explain the basic features of database access control and describe the issues involved when concurrency and database integrity must be maintained in a Web-based environment.<br />
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WebServer Updates And Concurrency In order to ensure that a WebServer transaction properly retrieves and updates information, we need to understand the differences between two processing modes: conversational and pseudoconversational (Figure 11.2). In a conversational mode, the unit of work is extended to include the entire wall-clock time that the user spends within the transaction. In pseudoconversational mode, the unit of work is partitioned. The duration of the task begins when the user requests a database service and ends when the database delivers the response to the user. The system then stands idle, releasing any locks that may have been held by the previous transaction. As we know, even though the Oracle WebServer Web Request Broker maintains the Oracle connection after each PL/SQL request, we must still understand how to preserve database integrity when updating Oracle from WebServer pages.<br />
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Figure 11.2 Example of WebServer connections. To illustrate, consider an example where a user displays order information, waits five minutes, then issues an update of the order information. If we process in full conversational mode, there is never a problem of database corruption because exclusive record locks are held for the entire duration of the terminal session. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch11/378-382.html (1 of 4)4/03/2005 6:16:17<br />
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However, the resources required to hold the locks may cause a burden on the database, and the lock will impede other transactions that want to retrieve (and possibly update) the information being held by the session. The solution to the locking problem is to process in pseudoconversational mode and release the record locks after the screen has been mapped out to the user. However, this processing mode can lead to a variety of problems. Releasing locks in a client/ server environment can be very desirable from a performance perspective, but the side effects must be addressed by the application. These side effects include: • Dirty reads—A dirty read is a situation where a record is retrieved by one transaction while being updated by another transaction. Assume that a transaction starts and grabs customer ABC with the intent to update. The information for ABC is displayed on the screen, and the user changes the value of the customer_status field. At this time, the change has been written to the database, but the information is not made permanent until either a commit or an abort statement is issued. During the original transaction, the change may be nullified with an abort statement. Unfortunately, a transaction may have read the value of customer_status for ABC before the transaction was aborted, thereby reading incorrect information. • Nonreproducible results—Nonreproducible results most commonly occur when a report is being run against a database that is actively being updated. The report may be run in local mode, a processing mode that bypasses the services of the database manager, ignoring all database locks and reading the database files directly from the disk. The local mode report sweeps the database pages obtaining the requested information, but it also reports on information while it is in the process of being changed. This can also result in phantom rows as rows are read while they are in the process of being deleted or added. Conversational processing is usually associated with a pessimistic locking scheme; that is, the transaction manager assumes that the transaction is going to be interfered with during the duration of the session, and the locks are held the entire time the record is being viewed. Pseudoconversational processing mode is associated with an optimistic locking scheme, whereby the system assumes that the transaction will remain isolated. Oracle Database Locking And Granularity Oracle database locking can take place at many levels. For Oracle relational databases, the locks can be set for an entire table within the tablespace or a row within the table, both of which are shown in Figure 11.3.<br />
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Figure 11.3 Example of Oracle locks. Oracle offers two types of locks: shared and exclusive. The most common type of locks are shared locks, which are issued with SQL select statements. Exclusive locks file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch11/378-382.html (2 of 4)4/03/2005 6:16:17<br />
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(sometimes called preemptive locks) are issued with delete and update statements. In shared locking, whenever a unit of data is retrieved from the database, an entry is placed in the database storage pool. A lock records the unit ID of the item being locked, which is usually a rowid or database page number. The lock consumes 4 bytes for each row stored in the Oracle shared pool. This lock will be held by the database until a commit, end, or abort message releases the lock. Most locking schemes use a coexistence method. For example, many clients may have shared locks against the same resource, but shared locks cannot coexist with exclusive locks. Whenever an update event occurs, the database attempts to post an exclusive lock against the target row. If any other tasks hold a shared lock against the target row, the exclusive lock will wait (see Figure 11.4).<br />
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Figure 11.4 Example of exclusive and shared locks. The locking scenario displayed in Figure 11.4 ensures that all database integrity is maintained and database updates do not inadvertently overlay prior updates. However, there is a penalty for maintaining shared locks. In most databases, a lock requires 4 bytes of RAM storage within the storage pool, and large SQL select statements can create SOS (Short On Storage) conditions that can cripple the database. For example, a select statement that retrieves 1,000 rows into the buffer will require 4,000 bytes of lock space. This condition can also cause the deadly embrace, or DB-KEY deadlocks. A deadlock condition occurs when two tasks are waiting on resources that one of the tasks has locked (see Figure 11.5).<br />
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Figure 11.5 Oracle deadlock example. Oracle only issues locks against rows when it needs to, so programmatic solutions can be used with WebServer applications to minimize the amount of locking used for very large update tasks. For example, in Oracle SQL, a programmer can use the select…for update clause to explicitly lock a row, or a set of rows, prior to issuing the update operation. This will cause the database to issue exclusive locks at the time of retrieval and hold these exclusive locks until the task has committed or ended. In the following SQL code, an exclusive lock is placed on the target row, and no other tasks will be able to retrieve that row until the update operation has completed: Select * from EMPLOYEE where emp_name = 'Burleson' for update of salary;<br />
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For large updates, statements can be issued to lock an entire table for the duration of an operation. This is useful when all rows in the table are going to be affected, as in the following salary adjustment routine. The nowait option will return control to you immediately, along with a message stating whether the table you are accessing is locked by another user. Without this option, Oracle would wait until the table became available, lock the table to perform an operation, and return control back to the user. The following snippet of code shows the use of the nowait statement: lock table EMP_TABLE in exclusive mode nowait; update EMP_TABLE set salary = salary * 1.1; There are times when the application wants to update all of the rows in a table, but it is not practical to lock the entire table. An alternative to the exclusive update is to use the SQL fetch statement to lock a small segment of the table, perform the update, and then release the locks with a commit statement, as shown in Listing 11.1. Listing 11.1 Using the fetch statement for an update. declare cursor total_cursor is select emp_name from EMP_TABLE; declare cursor update_cursor is<br />
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select rowid from EMP_TABLE where emp_name = :my_emp_name for update of salary; begin count = 0; open total_cursor; begin_loop; open update_cursor; fetch total_cursor into :my_emp_name; fetch update_cursor into :my_rowid; if (update_cursor%found) then { update EMP_TABLE set salary = salary * 1.1 where rowid = :my_rowid; count++; if (count = 20) then { commit; count = 0; } } close update_cursor; close total_cursor; end; As you can see, locks are set as the rows are fetched—20 at a time—and then released with a commit. This technique consumes less memory in the lock pool and allows other SQL statements to access other rows in the table while the update is in progress. Of course, if this code fails, it would need to be restarted from the point of the last commit statement. This requires additional logic to be inserted into the update program to record the rowid of the last commit ted row, and to restart the program from that row.<br />
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Determining The Lock Level Some other databases, such as DB2, attempt to alleviate locking problems by performing lock escalation. Lock escalation increases the granularity of the lock in an attempt to minimize the impact on the database lock manager. However, Oracle does not perform lock escalation. Therefore, any lock escalation must be performed manually by knowing the number of row locks that a transaction may hold. In Oracle, the level of locking is directly proportional to the type of update being executed. Remember, for row-level locking, a lock must be placed in the lock storage pool for file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch11/382-385.html (2 of 4)4/03/2005 6:16:18<br />
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every row that the SQL statement addresses. This can lead to very heavy resource consumption, especially for SQL statements that update numerous records in many tables. For example, an SQL query that selects many but not all of the records in a school’s REGISTRATION table might state: select * from REGISTRATION where REGISTRATION.grade = 'C'; Depending on the number of students affected, this type of query will begin to hold row locks until the task has successfully completed or until the SQL statement terminates due to a lack of space in the lock pool. However, if the database supports lock escalation, the database will set a single lock for the entire table, even if only a portion of the rows in registration are affected. If the statement select * from REGISTRATION is issued to return all rows in the REGISTRATION table, the database will escalate from row-level locking to pagelevel locking. If the REGISTRATION table resides in a single tablespace, some database engines will escalate to tablespace-level locking. This strategy can greatly reduce resource usage on the lock pool, but some lock mechanisms will escalate locks, even if it means that some rows are locked when they are not used by the large task. For example, select * from EMPLOYEE where department = ‘finance’ may cause the entire EMPLOYEE table to lock, preventing updates against employees in other departments. Whenever possible, large SQL updates should be run using table-level locks, thereby reducing resource consumption and improving the overall speed of the query. Some implementations of SQL provide extensions that allow for the explicit specification of the locking level and granularity. This mechanism could allow exclusive locks to be placed on a result set if the user intends to update the rows, or to turn off shared locks if the rows will never be updated. In Oracle, the engine must know that a row is free before altering any values within the row. The database accomplishes this by issuing an exclusive lock on the target row. The exclusive lock mechanism then sweeps the internal lock chain to see if shared locks are held by any other tasks for any rows in the database. If shared locks are detected, the update task will wait for the release of the shared locks until they are freed or until the maximum wait time has been exceeded. While the task is waiting for the other tasks to release their locks, it is possible that one of these tasks may issue an update. If this update affects the original task’s resources, a database deadlock will occur, and the database will abort the task holding the least amount of resources. Unlike object, network, or hierarchical databases, which update a single entity at a time, an Oracle database may update hundred of rows in a single statement. For example: update REGISTRATION set REGISTRATION.grade = 'A' where<br />
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course_id = 'CS101' and COURSE.instructor_id = 'BURLESON'; This single statement may update many rows, and the Oracle concurrency manager must check for contention (i.e., shared locks). If any other tasks are viewing any other rows in the database, the engine will set as many exclusive locks as it can and put the statement into a wait state until the shared locks from other tasks have been released. Only after the desired rows are free will the transaction be completed.<br />
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Alternative Integrity Mechanisms For WebServer The problems of lock pool resources and database deadlocks have lead to some creative alternatives to shared and exclusive locks. Locking can be turned off in any database by issuing a commit statement immediately after the select statement. Without long-term shared locks, lock pool utilization is reduced, and the potential for database deadlocks is eliminated. But, we still must deal with the problem of ensuring that updates are not overlaid. Consider the example of updates without locking shown in Figure 11.6.<br />
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Figure 11.6 Example of a menu model for a WebServer application. Both tasks have selected Burleson’s employee record and issued commit statements to release the locks. Task B now changes Burleson’s performance rating and issues an update, which writes the column back to the database. Task B, which is now looking at an obsolete copy of Burleson’s performance_flag, changes the salary, improperly assigning Burleson’s raise. This is a type of logical corruption whereby a user relies on outdated values in other rows, then updates the target column based upon the obsolete information.<br />
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Some databases, such as SQL/DS and Oracle, allow select for update commands. With select for update, the before image of the row is compared with the current image of the row before the update is allowed. However, since it is not recommended that Oracle WebServer applications use select for update, there are a couple of clever techniques you can use to release all Oracle locks and still maintain database integrity.<br />
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Issue All Updates With A where Clause For example, if Burleson’s row contains the performance_flag, salary, and name columns, each of the columns will be specified in the update command, even if the user has not changed the column (see Figure 11.7). Using this method, if any of the values have changed since the row was initially retrieved, the database will reject the transaction with a not found SQL code. The WebServer application could interpret this code, re-retrieve the updated record, and present it to the user with its new value.<br />
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Figure 11.7 A WebServer solution to update anomalies.<br />
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Note: It is very important to run the explain utility with this type of update statement to be sure that the SQL optimizer uses the employee index to locate the row. With so many items in the where clause, some optimizers may become confused and service the request by using a full-table scan, causing significant performance delays. Some implementations of SQL allow the programmer to specify the index that will be used to service the query, while other implementations of SQL require that the indexed field be specified first in the where clause. Regardless, it is important to run an explain plan on the SQL to be sure that the additions to the where clause do not impede performance.<br />
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Some databases have SQL extensions that can explicitly turn off unwanted indexes. Oracle, for example, allows indexes to be turned off by altering the key field used in the where clause. Assume that EMP_TABLE has the following definition: create table EMP_TABLE ( emp_name sex performance_flag salary<br />
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char(20), char(1), number, decimal(8,2));<br />
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Let’s further assume that emp_name has a unique index, and the fields sex, performance_flag, and salary have non-unique indexes. To ensure that the index on emp_name is used, the index key fields will be altered by concatenating a null string to the end of the char columns and adding a zero to the end of each numeric column. Hence, the SQL update would read:<br />
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Update EMP_TABLE set salary where emp_name performance_flag+0 sex !! "" salary+0<br />
<br />
=<br />
<br />
salary*1.05<br />
<br />
= = = =<br />
<br />
'Nally' 9 'M' 20000;<br />
<br />
and and and<br />
<br />
There is another method to ensure that the emp_name index will be used. We could alter the emp_name index to include the nonunique fields of sex, performance_flag, and salary, creating a large concatenated index on every column in the table. There would be a slight index overhead, but you can be assured that all index updates perform efficiently without relying on the SQL programmers to alter their SQL. Add A Date-Time Stamp To Each Row This solution requires that a date-time stamp column be added to each table that may be updated. All applications are required to select this column and include it in the where clause when issuing any update SQL. Of course, if the row has changed, the date-time stamps will not match, and the transaction will fail with a not found SQL code. WebServer Distributed Database Concurrency Whether the manager chooses to purchase an API or create a custom API, it is very important to realize that the nature of the data access can tremendously impact the complexity of the processing. For read-only databases, API processing is relatively simple, but for systems requiring cohesive updating, the processing problems increase exponentially. In fact, it is impossible to implement any cohesive updating scheme with 100 percent reliability. There is an inherent updating problem with distributed databases that is common to all systems. This particular updating problem occurs when a federated database attempts to simultaneously update two distributed databases. Commonly known as the twophase commit (2PC), the procedure is illustrated in the following example: Apply update A Apply update B If A-OK and B-OK Commit A <===="Here is the deadly exposure" Commit B Else Rollback A Rollback B As you can see, updates A and B get posted to the database. If the SQL code indicates that each transaction has completed successfully, then the system will issue commit statements to A and B. The point of exposure occurs when a failure happens after the commit of A but before the commit of B has been completed. Of course, the exposure<br />
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can only happen when the failure occurs at the exact instant between the commit of A and the commit of B, but it is an exposure that has a potential to cause a major loss of integrity within the database, and an exposure for which there is no automated recovery. The only remedy is to notify the DBA that the transaction has terminated and manually rollback the updates to A and B. This type of corruption has a very small probability, and most databases do not worry about this exposure.<br />
<br />
Summary Concurrency control has become a pressing issue due to the increasing popularity of client/server systems. As client/server systems become more mature, we will begin to see concurrency methods that can automatically manage updates to distributed databases. In the meantime, the developer must decide which of the update control mechanisms is best suited to the operation of their distributed database.<br />
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CHAPTER 12 Using Java And LiveHTML With Oracle WebServer The method for processing requests through the PL/SQL cartridge of Oracle WebServer is discussed in detail throughout the previous chapters of this book. In this chapter, we’ll discuss the other two major cartridge components of Oracle WebServer 2: the Java Interpreter and the LiveHTML Interpreter. The Java and LiveHTML cartridges work with the Web Request Broker to build dynamic content into Web pages. In addition, LiveHTML enables information to be included in documents from sources on the server, such as the output from executing Unix shell scripts.<br />
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Java Java is a very new technology that enables the execution of code (called applets) that can be distributed across heterogeneous computer nodes on the Internet. It provides an object-oriented, secure, portable, high-performance, full-featured development environment for generating interactive 3D Web documents, intelligent agents, and selfupdating software.<br />
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Note: Object-oriented computing is characterized as performing specific functions through modularized code that can be loaded dynamically on an asneeded basis. In addition, object-orientation involves the application of inheritance, polymorphism, encapsulation, and abstraction. For details on file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/391-393.html (1 of 3)4/03/2005 6:16:19<br />
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object-orientation, refer to Chapter 1, Evolution Of The Internet, The World Wide Web, And Databases.<br />
<br />
Java provides the ability to run the same applet on any machine that has a Java interpreter. In addition, Java has minimized the porting requirements of code down to only one applet for each application to interpret and execute. The dynamic presentation of Java applets on a Web page is a remarkable spectacle to behold. Instead of the basic hypermedia of text and images that we are accustomed to, the dazzling effects of these self-contained applications can be interactive in nature. To date, Java applets are used to animate image icons, so the Web page appears to be constantly in motion with dancing icons. Development Of Java As many of you are aware, Java is a product of Sun Microsystems. Its development began in 1991 as a special project named Green to sell software technology to consumer electronics companies. One of the key goals of the Green project was for the software code to be platform-independent, because developing for only one platform tremendously limits a product’s marketability. In addition, subsequent roll-outs to every other platform is a developer’s nightmare that often consumes too much capital to make the venture successful. The original name of the Java language was Oak, but the name had to be changed due to it not passing a trademark search. Java was initially intended to be developed using C++, but the primary developer, James Gosling, found its structure too complex for accomplishing their objectives. Originally, there were four components of the startup product including the language (Oak), an operating system called GreenOS, a user interface, and a hardware device, all fused together into a hand-held unit called *7. The first application for this technology was targeted on consumer electronics manufacturers to place the Sun logo on the front of television boxes. During this time, Time-Warner was soliciting the industry for set-top box operating systems and technology to provide video ondemand. The set-top box would be used to decode the data stream that entertainment companies would be sending to consumers for display on television sets. The Green project was renamed at this time to FirstPerson Inc. The focus of the Java project then shifted from the television market to the World Wide Web, which had the same need for small, platform-independent code. At about this time, the first graphical Web browser called Mosaic was released, and, for the first time, Web surfers enjoyed the merging of graphics and text into Web documents. The Web continued to grow at a staggering pace, mainly due to the improvement in bandwidth on the Internet. Seeing the potential market for their software expanding rapidly, substantial resources were brought to bear by Sun to finalize the development of the Java environment. During the latter half of 1994, a Web browser called HotJava was developed and was followed soon thereafter by the Java language. The public announcement of the Java environment occurred on May 23, 1995 at SunWorld ’95. Since that date, the fortunes of Java have continued to grow, due in large part to its incorporation into Netscape Navigator, the most popular browser on the Web.<br />
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Java And Portability Because of its interpretative nature, Java is a programming language that can execute on any computer. Java begins as Java source code, which must be compiled into Java Virtual Machine bytecode before it can be transmitted to a receiving host machine. When a client receives a Java bytecode applet, the Java Interpreter is invoked to translate the bytecode into the native machine code for the receiving client. Thus, Java is both compiled (at creation time) and interpreted (at execution time). (See Figure 12.1.)<br />
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Figure 12.1 The interpretative process of Java. Java is an interpretive language that requires the computer running it to have a Java interpreter to convert the Java code into the computer’s machine code. Because Java is an interpretive language, the Java code does not have to conform to each and every hardware platform. The Java compiler generates executable code from the source code by first compiling for a hypothetical machine called the Java Virtual Machine, which resides on the computer where the applet is to be executed. Some of the operating systems that currently support the Virtual Machine include Windows, Solaris, MacOS, OS/2, Linux, Amigo, and a few others. Language interpreters have traditionally suffered from poor response time, but Java has improved this process by compiling to an intermediate stage (the Virtual Machine), where the source code is converted to bytecode. This bytecode is not executable by any machine, but must be converted to the native code for a specific machine to understand. This feature of easily converting file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/393-396.html (1 of 3)4/03/2005 6:16:20<br />
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to machine language is one of the positive performance aspects of Java. By porting a language interpreter to a machine, you are ensuring that the compiled code will execute on that platform. The portability of Java is not only enabled by the virtual machine specification, but also by the requirement that data sizes will always consume the same amount of space, regardless of the host computer. In Java, datatypes (such as integer) are specified in only one length. This is not the case for C programming languages that may change depending on the underlying hardware and operating system. For instance, an integer that has a length of 16 bits in Windows 3.1 now requires 32 bits in Windows 95. Computer processors have the same inconsistency in this area, which is illustrated by the Intel 486 being defined as a 32-bit machine and the DEC Alpha as a 64-bit machine. Because data sizes are always the same within Java, the programs are hardware-independent. Java has often been described as C++ without the pointers. One of the other portability issues that differentiate Java from C++ is that C++ allows the use of pointers to directly access memory locations. In addition, Java does not allow automatic memory management. Because Java does not use pointers, there is less likelihood that portions of memory could be corrupted by faulty addressing. However, the lack of pointers makes Java far less robust than C++. It is impossible to link Java objects together, and each Java class must encapsulate all of the functionality that it requires. Memory management within Java is accomplished by the program keeping track of objects and references to those objects. When an object has no more references, it is removed from memory by a job running in the background. Object Orientation Of Java The object-oriented design of Java is one of its best attributes and is certainly in line with the future direction of application code. Object-oriented code has several benefits, including: • Abstract datatypes—ADTs allow a data field to contain a conglomeration of many different datatypes. For example, a datatype called Address could be defined to contain two string datatypes for street and city address, and a numeric element called zip_code. These three subelements become a part of the datatype and are treated by Java as a full-fledged datatype. • Inheritance—Inheritance is the ability of a Java object to inherit the data structures and methods for all associated classes that reside above it in the class hierarchy. • Polymorphism—Polymorphism is the ability of different objects to receive the same message and behave in different ways. • Reusability of code—Reusability of code results from the ability of an objectoriented language to encapsulate procedures according to function. The basic element of object-oriented programming (OOP) is the object. An object is created in the Java language from a class. The class is the basic execution unit and is comprised of variables and methods to form a reusable process. In object-oriented parlance, the class incorporates data items and behaviors (sometimes called methods) into its software composition. This process of binding the class instructions is referred to as encapsulation. Once a class is built, it can be used again to create other file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/393-396.html (2 of 3)4/03/2005 6:16:20<br />
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functional classes. The classes can be dynamically loaded whenever they are needed to perform repetitive processes. The Java applications can alter their functionality by linking additional classes at any time to perform other tasks. The class definition is used twice during the life of a Java object. The class definition is first used at object creation time to define the data structures for the object, and then is referenced at runtime when a behavior is requested. Every object has a state, which is its status at a given point in time. For example, the state of the object radio could be one of the following: • • • •<br />
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Radio on Radio on and tuned Radio on and not tuned Radio off<br />
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The state of a class is represented by instance variables that are managed locally by a specific class and, in most cases, are not globally available to other classes. Changing the state of the class is accomplished through methods, which are associated with a specific class, just like the local instance variables. In other words, the method is the code that performs functions for the class to modify its status. In the example for the radio object, a method could be the radio buttons to turn the radio on or off, or to tune the stations. Another base feature of the object-oriented environment is inheritance. Let’s say that the radio class was originally defined as an AM radio. Instead of writing a whole new set of code to define the radio for FM, you could simply create the new FM radio class and have it inherit the properties of the AM radio class. Then, you would only need to make minor code adjustments to change AM to FM. This new class would be referred to as a subclass of the original class, which is now described as a superclass of the new one. This relationship between subclasses and superclasses can save tremendous amounts of time in coding extensions to the functionality of existing objects, because all objects inherit the data definitions and behaviors of their superclasses. Within the Java class, variables and methods are accessed via the following privilege categories: • Public—Any class can access the variables and methods. • Private—Methods can only be referenced by a specific class. • Protected—Variables can only be utilized by methods in that specific class and any of its subclasses.<br />
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• Friendly—Allows all packages in the same package to use the methods and variables. This is the default category for access if none is specified.<br />
<br />
Note: The Java package is a grouping of classes with common functionality. This concept is similar to that of PL/SQL packages used within Oracle WebServer, where related functions and procedures are maintained together as a package. Chapter 8, WebServer’s OWA Utilities, has several examples of using Oracle PL/SQL packages.<br />
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Security Of Java There are several features of Java that enhance the security of distributed processing, including a bytecode verifier, runtime memory layout, and restrictions on file access. When the interpreter receives the Java bytecode, it reviews it for language compliance. This is done to ensure that the code was not altered since it was compiled, which sometimes occurs inadvertently. If the code passes this step, then the interpreter defines the memory layout for the classes. Because the memory layout is dynamically created for a specific computer configuration, the chances of a surfer guessing the structure of a class for unauthorized access is minimized. After the memory layout is generated, the interpreter reviews the intended file accesses of the loaded classes. If the file accesses are inconsistent with those permitted by the client, then the request is rejected. Performance Of Java The performance of Java compared to other interpretive languages is greatly improved based on some of its properties that reduce the overhead it must deal with. These include: • Multithreading • Efficiency of bytecode • Linking of native C code In single-threaded applications, programs must wait for user input, file availability, and network access. During the times that the applications are waiting, the processor is idle, because it has no requests to process. Requests become bottlenecked in a queue behind the first process waiting for resources. On the other hand, Java can break down a request into several different processes that execute independently and simultaneously, which provides much greater efficiency in process throughput. The tools for managing the threads are built into Java, thus reducing the reliance on the operating system for this feature. Another positive performance feature is that the compiled Java bytecode is very similar to native machine code, so the process of interpreting this code is very efficient and straightforward. This certainly was the intention of Java developers—to make the conversion a simple task on any machine and to minimize the machine resources allocated to the task. Finally, Java provides an option to link native C code into an application. This is very file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/396-398.html (2 of 3)4/03/2005 6:16:20<br />
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efficient and provides a faster implementation than having to compile code at runtime. Of course, more work is involved for the programmer, who would have to incorporate the linking component into the code.<br />
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Fundamentals Of Java Code The file containing the Java source code should have the extension .JAVA appended to the file name. Java source code is the code that will be compiled to bytecode. Java programs can contain several of these compiled units. Compiled units in Java are defined with any of the following four structure elements: • • • •<br />
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Package statements Import statements Class declarations Interface definitions<br />
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The class declaration is used extensively for specifying instance variables and methods, as well as static variables and methods.<br />
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Note: Static variables are available to all occurrences of a class being executed, whose values do not change. Static methods provide global functions associated with a specific class. The definition of static variables and methods will contain the string static in its syntax.<br />
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All source code must have a main() method defined; this indicates to the interpreter where to start running the program. The basic structural elements of Java source code are outlined in Listing 12.1. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/398-401.html (1 of 4)4/03/2005 6:16:21<br />
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Listing 12.1 Sample Java code elements. import classname class classname { public static void main (String args[]) { // source code } } The source code is added into the main() method, which receives arguments from the interpreter (String args[]). The method does not return any variables (void), is the same for all occurrences of the class (static), and can be executed by any class (public). If the program requires the use of this method, then the import statement is needed to load in the previously compiled class code. The import statement can also import C code and Java packages, and allows code to be loaded into the applet for use in a number of places. Importing a package will load all classes within that package into the program. Packages can be utilized by specifying a fully qualified class name for the class to be executed. This name is comprised of the class name appended to the end of the package name. An example of code using the class Date within package java.util is presented in Listing 12.2. Listing 12.2 Example code using Java class. java.util.Date todaydt = new java.util.Date(); System.out.println(todaydt); Using the fully qualified class name is useful for loading a class from a package into one location in a program, and also when you only want to load one class from a package. An interface is a specially defined class. Interfaces are similar to normal classes because they also contain methods and variables. However, interfaces are different because they are always abstract. Even though methods are defined in an interface, the code comprising the method is not. The variables in the interface are static in nature and are used in interfaces only as constants. Classes can inherit from only one superclass but can inherit from multiple interfaces. So a common location for using interfaces is within subclasses. A skeletal definition for an interface definition appears in Listing 12.3. Listing 12.3 Example code for an interface definition. interface interface_name [extends interface_name]{ [variable declaration;] [method declaration;] }<br />
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The interface definition is similar to the class definition, but there are some differences. First of all, the interface keyword is used instead of the class keyword in the definition statement. Secondly, interfaces can extend other interfaces through the use of the extends keyword. Interfaces have an inheritance chain just like classes, whereby interfaces can be subclassed by using the extends keyword in the definition. For instance, you could put all your constant values into one interface, so that they could be used in classes that do not need to implement a method. An example of such an interface appears in Listing 12.4. Listing 12.4 An example of an interface containing constants. public interface proc_constants int outer_width = 25; int inner_width = 25; int outer_length = 40; int inner_length = 40; int outer_height = 60; int inner_height = 50; }<br />
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{<br />
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To define an interface class (Build_matl) using constants (proc_constants) and a method (order_lumber) would extend the interface, as shown in Listing 12.5. Listing 12.5 Sample interface extended for constants and a method. interface Build_matl extends proc_constants { void order_lumber (int parm1, int parm2); } To reference the interfaces Build_matl and item_cost within the class Classname, the implements keyword is used, as displayed in Listing 12.6. Listing 12.6 Sample class referencing interfaces. public class Classname extends Superclass implements Build_matl, item_cost { // class body }<br />
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Oracle WebServer’s Java Implementation The Java Interpreter is the cartridge within Oracle WebServer that allows for the execution of Java on the server to generate dynamic Web documents. In Oracle WebServer 3.0, Java is used to create and maintain Web pages, such that the WebServer is only required to refresh the data portions of a Web page.<br />
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Note: Remember that cartridges used by the Web Request Broker to build different functionality into Web pages include the PL/SQL Agent, the Java Interpreter, and the LiveHTML Interpreter. Of the three cartridges, the Java Interpreter has the best and most varied functionality, while the PL/SQL Agent provides the most efficient database access method. The LiveHTML Interpreter is Oracle WebServer’s implementation of Server Side Includes (SSI), which enables the output from programs executed by the operating system to be inserted into Web pages.<br />
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As mentioned previously, Java applets (or applications) are comprised of code modules that can be downloaded from the Internet in realtime and executed locally on the client.<br />
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connection to the Internet. The NC would not have a hard drive or a floppy disk drive, instead relying on the Internet for applications, such as Java applets and storage.<br />
<br />
Downloaded Java applets have the ability to interface with other applets, and applications can be built on a combination of these applets from across the Internet. Remember, it is the bytecode created by the compilation of Java source code that is transferred throughout the Web. Running Java On The Client Or Server Oracle WebServer enables the execution of Java either on the client or on the server. (See Figure 12.2.) It is possible to embed calls to Java applets within Web pages that can be executed by any Java-enabled browser. A good way to implement client-side Java applications is to store the code on the file system of the local operating system, and then execute it on an as-needed basis.<br />
<br />
Figure 12.2 Java and client/server architecture. Server-side execution of Java within Oracle WebServer is enabled by the Web Request Broker, which processes the requests using the WRB API in conjunction with the Java Interpreter cartridge. The Java Interpreter cartridge is very adept at manipulating graphical images—something the other cartridges lack. Java is an excellent tool for building image maps (defined earlier in the book as a clickable image). Actually, several images may be merged to form a super image, where each section of the image represents a hotspot for initiating different requests. After executing a request, the WRB returns the output to the Oracle Web Listener, which subsequently sends the output to the requesting Web browser. Using PL/SQL With Java Java can execute the PL/SQL code stored in an Oracle database by initiating a process through the Java Interpreter component of Oracle WebServer. In this scenario, the Java Interpreter does not utilize the PL/SQL Agent to satisfy the incoming HTTP request against the database, as is the case with PL/SQL requests that are mapped directly through the PL/SQL Agent. The PL/SQL code to be executed is stored in the Oracle database and thus could be ported to any other Oracle database for processing on a different server. This feature provides developers with the flexibility to build their WebServer applications by sharing code across different applications on Oracle instances, as well as porting the applications easily through the system development life cycle, from development to production. As you remember, Java applets are also portable to any platform due to the compilation of its source code for the Java Virtual Machine. The combination of both the PL/SQL and Java code being highly portable makes Oracle<br />
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WebServer a powerful tool for developing Web applications because the whole idea of the Web is to share information easily and rapidly.<br />
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Oracle WebServer’s Java Interpreter The Java Interpreter is the mechanism that interprets and executes Java code within Oracle WebServer on any platform. There is no additional software installation required to use the Java Interpreter for executing Java code; the installation of Oracle WebServer includes this component.<br />
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Note: If you want to interpret JavaScript, you must download the JavaScript Interpreter from www.javasoft.com.<br />
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The server-side requests processed through the Java Interpreter are via the Web Request Broker, which dispatches them to the cartridge. Using the WRB as the gateway interface for these requests is determined by your virtual directory mappings for the WRB that are defined through the WebServer Administrator Web page. In essence, these virtual directories are associated with the physical directories of the underlying file system.<br />
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Note: You can find additional information about virtual directory mappings for WRB and Oracle Web Listener in Chapter 4, Installing And Configuring Oracle WebServer.<br />
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Once a request is executed, the results are returned to the initiating browser through the services of the Oracle Web Listener. Oracle WebServer provides a set of Java packages called the Java Web Toolkit, which contains classes that are extremely helpful in building Java applications. This toolkit is similar to the PL/SQL Web Toolkit that provides the hypertext functions, hypertext procedures, and OWA utilities included in packages such as owa_util and owa_text. The Java applications are dynamically defined for interaction between browsers and databases. As mentioned earlier, PL/SQL packages can be executed from within Java code to capitalize on the relative strengths of both languages. Java is a very creative tool for managing graphical images, while PL/SQL provides more efficient database access. The Java Web file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/404-406.html (1 of 2)4/03/2005 6:16:23<br />
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Toolkit has wrappers for Java applets. Wrappers enable the storage of applets in Oracle databases. This feature provides the basis for client-side computing, where the Java Interpreter retrieves wrapped applets from a database and transfers the code to a browser on the client workstation. The applets are then embedded into a Web page and subsequently executed. Processing on the client side can also be accomplished through the PL/SQL Agent in a special situation where the applets are retrieved as data. Java code may load classes from the Java Web Toolkit by using the import statement, discussed earlier in this chapter. The groupings of classes to be imported include: • oracle.rdbms—Classes for accessing a database • oracle.html—Classes for generating dynamic HTML • oracle.plsql—Classes for processing PL/SQL Accessing Oracle Databases From Java Up until now, all previous database access using PL/SQL code described in this book has involved the PL/SQL Agent. This is not the case with the execution of PL/SQL from Java, which bypasses the PL/ SQL Agent altogether. If the PL/SQL Agent was processing a request through the Web Request Broker, then the database connection was maintained for the duration of the request’s processing. The execution of PL/SQL code within Java is similar to CGI, in that a database connection is initiated for every request and will add more overhead to the operation. The Database Connection Descriptors were configured for the Oracle WebServer only and apply to the PL/SQL Agent for defining the privileges associated with an application. On the other hand, database connections for Java are specified directly in the code. Using PL/SQL Package Wrappers Accessing an Oracle database through the Java Interpreter is accomplished by executing PL/SQL within the database. PL/SQL code can be represented as PL/SQL packages or standalone PL/SQL procedures and functions. Standalone procedures and functions are those that are not grouped under a package. PL/ SQL packages must have a package wrapper to interface with Java. The package wrapper becomes a Java class that contains methods for executing the functions and procedures grouped in that package. Only one wrapper can contain all of the standalone procedures and functions. To create a package wrapper for a PL/SQL package, execute the pl2java utility as shown here: pl2java<br />
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You can specify one or more package names for the pl2java utility to create as wrapper classes. Every time an applet is executed, an instance of the class will be created to process against the related package. Separate instances of the class are created to keep the values of local variables distinct from instance to instance and to allow flexibility in the selection of methods to process. Global variables may also be used to share data values across class instances. Standalone procedures and functions can be wrapped with the pl2java utility by not specifying a package name and using the class flags argument. As previously discussed, all standalone procedures and functions should be contained in one wrapper class. The arguments for the pl2java utility are explained as follows: • flags—This argument determines how the wrappers will be built. All flags are optional except class, which may be required in specific situations. The various flags include: • directory_name—Wrapper classes will be stored in the directory specified by this flag. If this flag is not specified, the current directory will be the default location for the wrapper classes. • help—This flag provides useful information to assist the user. • class class_name—This flag assigns the package wrapper to a Java class and is required for wrappers of standalone functions and procedures. No wrapper name is specified for standalone functions and procedures because they are not grouped within a package. The class flag is optional for assigning packages to Java classes because Java class names default to the name of the package being captured. • package packagename—This flag specifies the name of the Java package that the wrapper classes are assigned to. • username—This argument is the name of the Oracle account that owns the packages. • password—This argument is the password for the database Oracle account that owns the packages. • connect_string—This argument specifies the processing information used to connect to the database where the packages reside. The Oracle System ID (SID) must be specified for accessing a local database. Accessing a remote database requires information such as the SID and hostname. • packagename—This argument specifies one or more package names to be assigned to a package wrapper. The package name is not specified for standalone functions and procedures, but the class flag argument is required to name the Java class wrapper. There are several PL/SQL packages that can cause the pl2java utility to fail when creating a package<br />
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wrapper. These incompatible datatypes, along with their replacement datatypes, can be seen in Table 12.1. Table 12.1Incompatible and substitute PL/SQL datatypes for the pl2javautility. Invalid Datatype<br />
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Replacement Datatype<br />
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PL/SQL Table: Boolean<br />
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Number PL/SQL Table<br />
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PL/SQL Table: Binary Integer<br />
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Number PL/SQL Table<br />
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PL/SQL Table: Positive<br />
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Number PL/SQL Table<br />
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PL/SQL Table: Natural<br />
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Number PL/SQL Table<br />
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PL/SQL Table: Long<br />
<br />
Varchar2 PL/SQL Table<br />
<br />
Positive<br />
<br />
Binary Integer<br />
<br />
Note: PL/SQL datatypes that are incompatible with package wrappers and have no replacement datatypes include rowid and mslabel.<br />
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Oracle Database Retrieval By Java An example of accessing data in an Oracle database using Oracle WebServer PL/SQL packages was presented in Chapter 8, WebServer’s OWA Utilities. Now, we will retrieve Oracle data using PL/SQL packages from within Java code. Here, we are utilizing the strength of the PL/SQL packages—efficient database access—combined with the versatility of the Java language. Listing 12.7 displays code for the PL/SQL package Hosts, which contains the procedure list_hosts. This procedure will perform an SQL query from within the PL/SQL code for its package body found in Listing 12.8. The data retrieved from table HOST (shown in Listing 12.9) includes host names, Oracle CSI numbers, and a count of the hosts associated with the same customer. Listing 12.7 PL/SQL code for the package Hosts. create or replace package Hosts as type string_table is table of varchar2(15) index by binary_integer; type number_table is table of number(10) index by binary_integer; function count_hosts (custname in varchar2) return number; procedure list_hosts custname in hostname out oracle_csi_nbr out ); end;<br />
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( varchar2, string_table, number_table<br />
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/ show errors Listing 12.8 PL/SQL code for the package body Hosts. create or replace package body Hosts as function count_hosts (custname in varchar2) return number as hostcount number; begin<br />
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select into from where<br />
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count(*) hostcount host cust_name = custname;<br />
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return hostcount; end; procedure list_hosts( custname in varchar2, hostname out string_table, oracle_csi_nbr out number_table ) as i number; cursor host_rcd (custname varchar2) is select host_name, oracle_csi_nbr from host where cust_name = custname; begin i := 1; for hosts in host_rcd (custname) loop hostname(i) := hosts.host_name; oracle_csi_nbr(i) := hosts.oracle_csi_nbr; i := i + 1; end loop; end; end; / show errors Listing 12.9 Oracle table HOST. create table HOST( host_name ip_address cust_name os_type os_version oracle_csi_nbr dba_pager_nbr ) pctfree 10 initrans 1 tablespace users01 storage ( initial 100k next 100k minextents 1 maxextents 121 pctincrease 0 ) ;<br />
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VARCHAR2(30) VARCHAR2(30) VARCHAR2(30) VARCHAR2(15) VARCHAR2(15), VARCHAR2(15), VARCHAR2(15)<br />
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NOT NOT NOT NOT<br />
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You can then create a main program for the Java code stored in the file HostRpt.java, as shown in Listing 12.10. The oracle.html package imported into the program will assist in the generation of dynamic HTML. Listing 12.10 Main Java program called HostRpt. import oracle.html.*; public class HostRpt { public static HtmlHead hd HtmlBody bd HtmlPage hp<br />
<br />
void main (String args[]) { = new HtmlHead ("Host List"); = new HtmlBody (); = new HtmlPage (hd, bd);<br />
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hp.printHeader (); hp.print (); } } Execute the pl2java utility to create a Java class wrapper for the Hosts package, as follows: pl2java username/password[@connect string] Hosts The output code from this utility will be generated into the Hosts.class file on the current directory, as illustrated in Listing 12.11. Listing 12.11 Java wrapper class Hosts.class. public class Hosts { public Hosts (Session session) { ... } public PDouble count_hosts (PStringBuffer custname) throws ServerException { ... } public void list_hosts (PStringBuffer custname, PStringBuffer hostname [], Pdouble oracle_csi_nbr[]) file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/410-412.html (1 of 3)4/03/2005 6:16:24<br />
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throws ServerException { ... } }<br />
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Note: If you encounter the error pl2java: java cannot be executed when running pl2java, then you have incompatibility between your JDK (which is the Java library) and the Oracle Java interpreter. You may need to download a different version of the JDK from the Web site www.javasoft.com. The untarring of this downloaded file will create a bin directory, which then needs to be added to your environmental variable path. Refer to Oracle bug 373840 for further details on this incompatibility problem.<br />
<br />
In order to connect to the Oracle database, a Session object must be created by modifying the main program, as shown in Listing 12.12. Importing the package oracle.rdbms into the program will make multiple classes with database functionality available. Session properties are defined for the environmental variables ORACLE_HOME and TNS_ADMIN using the Session.setProperty function. The variable ORACLE_HOME specifies the location of the Oracle software executables, and the TNS_ADMIN variable indicates the location of the SQL*Net V2 files tnsnames.ora and listener.ora for configuring client/server access. The session information specified for the database login includes the Oracle account, password, and connect_string. To assist in trapping exception conditions, the login process is enclosed within a try/catch block. Listing 12.12 Connecting to the database via the main program HostRpt. import oracle.html.*; import oracle.rdbms.*; public class HostRpt { public static void main (String args[]) { HtmlHead hd = new HtmlHead ("Host List"); HtmlBody bd = new HtmlBody (); HtmlPage hp = new HtmlPage (hd, bd); hp.printHeader(); Session.setProperty("ORACLE_HOME", “/opt/oracle/app/oracle/product/7.3.2”); Session.setProperty("TNS_ADMIN", “/opt/oracle/app/oracle/product/7.3.2/network/admin”); Session.session; try { session = new Session ("www_user", “passwd”, “connect_string”); } catch (ServerException e) { bd.addItem (new SimpleItem("Logon fails: ” + e.getSqlerrm())); hp.print(); return; } hp.print (); } } A new instance of the Java wrapper class now needs to be created with methods that will be used to call the procedures and functions within the Hosts package. Before you can call the stored procedures or functions of the Hosts package, Java instance variables must be defined for the PL/SQL parameters. An example of a PL/SQL parameter in this scenario is pCustname. In order to make the transition from generic Oracle PL/SQL code to Javawrapped PL/SQL, the PL/SQL tables need to be redefined as Java arrays. This Java class code is displayed in Listing 12.13 for program HostRpt. An additional set of WebServer Java classes called oracle.plsql is imported into the program to manage PL/SQL datatypes. The new instance of the Hosts package is generated by the statement Hosts hosts = new Hosts (session); where Hosts is the package name, and hosts represents a field name for the name of the host.<br />
<br />
Note: If you retrieve a PL/SQL value using the value methods, such as doubleValue() of pDouble, it is a good idea to first validate that the value is not NULL because an error condition will be returned for NullValueException. The other option would be to handle the NullValueException through the try function.<br />
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Sometimes Java will delay its internal cleanup processes before disconnecting the current session. This delay will hold previously allocated machine resources until the session is terminated so you should log off your session at the end of the wrapper class code. Listing 12.13 Wrapper class code for calling the Hosts package within program HostRpt. import oracle.html.*; import oracle.rdbms.*; import oracle.plsql.*; public class HostRpt { public static void main (String args[]) { HtmlHead hd = new HtmlHead (“Host List"); HtmlBody bd = new HtmlBody (); HtmlPage hp = new HtmlPage (hd, bd); hp.printHeader(); Session.setProperty("ORACLE_HOME", “/opt/oracle/app/oracle/product/7.3.2”); Session.setProperty("TNS_ADMIN", “/opt/oracle/app/oracle/product/7.3.2/network/admin”); Session.session; try { session = new Session ("www_user", “passwd”, “connect_string”); } catch (ServerException e) { bd.addItem (new SimpleItem("Logon fails: ” + e.getSqlerrm())); hp.print(); return; } Hosts hosts = new Hosts (session); String custname = null; if ((args.length < 1) || !args[0].startsWith(“CUST=")) { bd.addItem(new SimpleItem ("No customer name provided")); hp.print ();<br />
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return; } else { custname = args[0].substring(5); } // This section of code will capture PL/SQL parameter values PStringBuffer pCustname = new PStringBuffer (30, custname); PStringBuffer pHostname[]; PDouble pOracle_csi_nbr[]; PDouble pHostcount; // The following code will display a heading for the report bd.addItem("Customer ” + pCustname + “:") .addItem(SimpleItem.Paragraph); // Count the number of hosts by calling the Hosts package try { PHostcount = hosts.count_hosts(pCustname); } catch (ServerException e) { bd.addItem("Not successful in retrieving Host info for Customer ” + custname + “: ” + e.getSqlerrm ()); hp.print (); return; } int hostcount = (int)pHostcount.doubleValue (); if (hostcount == 0) { bd.addItem(“Host not associated with customer ” + custname); hp.print (); return; } // Build the empty arrays for holding the host names // and Oracle CSI numbers pHostname = new PStringBuffer [hostcount]; pOracle_csi_nbr = new PDouble [hostcount]; // Build the buffers for host data for (int i = 0; i < hostcount; i++) { pHostname [i] = new PStringBuffer (30); pOracle_csi_number[i] = new PDouble (); } // Retrieve host information by customer through the // execution of the Hosts package try { hosts.list_hosts (pCustname, pHostname, pOracle_csi_nbr); } catch (ServerException e) { bd.addItem (“Could not find host info for customer ” + custname + “: ” + e.getSqlerrm()); hp.print(); return; } // Create a report of the host names associated with the customers DynamicTable tab = new DynamicTable (2); TableRow row = new TableRow (); row.addCell (new TableHeaderCell (“Host Name")) .addCell (new TableHeaderCell ("Employee Number")); tab.addRow (row); for (int i = 0; i < hostcount; i++) { row = new TableRow (); if (pEmployeeNumber[i] .isNull ())<br />
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row.addCell (new TableDataCell (pHostname [i] .toString ())) .addCell (new TableDataCell ("New Host")); else row.addCell (new TableDataCell (pHostname [i] .toString ())) .addCell (new TableDataCell (pOracle_csi_nbr [i] .toString ())); tab.addRow (row); } hp.addItem (tab); hp.print(); // Disconnect from the database try { session.logoff (); } catch (ServerException e); } } Dynamic HTML Generation By WebServer Java As with PL/SQL stored procedures, dynamic HTML documents can be created through Java by utilizing the IHtmlItem interface against Java objects. Java interfaces were discussed in more detail earlier in this chapter. The specific interface IHtmlItem has two methods (toHTML and print) that in combination will convert the content of objects to HTML. The toHTML method builds HTML documents in the format of a string, within a buffer cache, which can be manipulated further from within the class code. The print method extracts HTML from a buffer and outputs the resultant Web page to system output via environment variables.<br />
<br />
Note: The Oracle package oracle.html contains numerous Java classes to assist your development of dynamic documents. You can also create home-grown HTML classes by deriving them from the Container and CompoundItem classes. This derivation of properties from existing classes is known as inheritance in object-oriented parlance.<br />
<br />
Just as hypertext procedures and functions (htp and htf) generate HTML tags for the creation of HTML documents, there are also Java objects that generate dynamic HTML Web pages. Table 12.2 shows these Java objects and the HTML tags they create. A skeletal HTML document can be built with the HTMLHead, HTMLPage, and HTMLBody objects. To incorporate the structural elements of the Web page, utilize the AddItem method for adding HTMLItems to the document body. Table 12.2WebServer Java objects that generate HTML tags. Java Objects<br />
<br />
HTML Elements<br />
<br />
HTML Body<br />
<br />
body of document<br />
<br />
HTMLPage<br />
<br />
page breaks<br />
<br />
HTMLHead<br />
<br />
document headings<br />
<br />
Table; DynamicTable; TableRow; TableCell; TableDataCell; TableHeaderCell; TableRowCell<br />
<br />
tables<br />
<br />
Comment<br />
<br />
comments<br />
<br />
Form<br />
<br />
HTML form<br />
<br />
Checkbox<br />
<br />
checkbox buttons<br />
<br />
Radio<br />
<br />
radio buttons<br />
<br />
Link<br />
<br />
hyperlinks<br />
<br />
Select; Option<br />
<br />
selection lists<br />
<br />
Anchor<br />
<br />
anchors<br />
<br />
Image<br />
<br />
images<br />
<br />
Hidden<br />
<br />
hidden fields<br />
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PasswordField<br />
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nondisplayed fields<br />
<br />
TextArea; TextField<br />
<br />
text areas<br />
<br />
Applet<br />
<br />
Java applets on the client<br />
<br />
Several classes for lists<br />
<br />
menu lists, definition lists, etc.<br />
<br />
Frameset; Frame<br />
<br />
frames<br />
<br />
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Java HTML Examples Notice in Table 12.2 that various lists can be generated through dynamic Java HTML. Listing 12.14 displays Java code that will create an ordered list. Listing 12.14 Java code for creating the OrderedList object. // We are about to create an ordered list OrderedList orderedlist = new OrderedList (); //Specify items to be added to this list orderedlist.addItem(new SimpleItem("Item One")) .addItem(new SimpleItem("Item Two")); //Now add the ordered list object to the body of the Java code bd.addItem(orderedlist); Listing 12.15 shows the Java code necessary to generate a menu list. The Java code used to create menu lists is very similar to the code used to create ordered lists. Listing 12.15 Java code for a menu list. // Create the MenuList Object MenuList menulist = new MenuList (); //Indicate the items to be added to the menu list menulist.addItem(new SimpleItem("Item One")) .addItem(new SimpleItem("Item Two")) .addItem(new SimpleItem("Item Three")); //Insert the MenuList object into the body of the Java code bd.addItem(menulist);<br />
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The code to create a definition list is a little different from the two previous lists in that the list is derived from the Container object, as displayed in Listing 12.16. Listing 12.16 Java code for a definition list. // Derive a new Container Object Container dterms = new Container (); dterms.addItem(new SimpleItem("Definition Item1")) .addItem(new SimpleItem("Definition Item2")) .addItem(new SimpleItem("Definition Item3")); DefinitionList dl = new DefinitionList (); //Create the new Object dl.addDef(dterms, new SimpleItem("DefList")); Listing 12.17 shows the code to create an HTML document. The package oracle.html is imported into the code to assist in the development of the document. Listing 12.17 Java code to generate a Web page. import oracle.html.*; public class Rochester { public static void main (String args[]) { //Build the HTMLHead Object “Rochester Institute of Technology” //for the document header HtmlHead hd = new HtmlHead ("Rochester Institute of Technology"); //Create the body of the document through the HtmlBody Object HtmlBody bd = new HtmlBody(); //Build the Object HtmlPage for the Web page HtmlPage hp = new HtmlPage (hd, bd); //Define the text to be displayed on the Web page bd.addItem("Rochester Institute of Technology"); //Print the page hp.print(); } } To create an HTML table, see Listing 12.18 for the pertinent Java code. Listing 12.18 Java code for creating an HTML table. //This example includes functions that were previously created Customer customer = getNewCustomer(); //Build a table defined with three columns DynamicTable tab = new DynamicTable (3); //Build the rows in the table TableRow rows[] = new TableRow[NUM_ROWS]; for (int i=0; i < NUM_ROWS; i++) {<br />
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//Define TableRow rows[i] = new TableRow(); // Insert data into the three columns of the row rows[i] .addCell (new TableHeaderCell (customer.getCustName())) .addCell (new TableDataCell (customer.getCustAddr())) .addCell (new TableDataCell (customer.getCustID())); //Insert the row into the table tab.addRow(rows[i]); } An HTML anchor can be created by using the Java code illustrated in Listing 12.19. Listing 12.19 Java code for creating an HTML anchor. Anchor anchor = new Anchor ("expire_date", new SimpleItem ("Expire Date: 01/98")); An HTML form is generated from the Java code shown in Listing 12.20. The form is defined with the GET method and uses the HTTP protocol. Listing 12.20 Java code used to generate an HTML form. //An object for the form is created as follows Form form = new Form ("GET", “http://www.BuffaloStateCollege.com/wrb/dormcheck”); //A textfield object needs to be built and inserted into the form form.addItem(new TextField("textfield")); //The form object built above is now inserted into the object HtmlBody bd.addItem(form); Listing 12.21 displays the Java code for executing a client-side Java bytecode applet in a Web document. The applet file named LilacFest.class processes a parameter and displays text within an applet window defined with the dimensions of 350 by 50. Listing 12.21 Executing a client-side Java applet. Applet applet = new Applet ("LilacFest.class", 350, 50); applet.addParam("flower", “Welcome to the Lilac Festival”);<br />
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LiveHTML LiveHTML is a very useful tool within Oracle WebServer. Essentially, LiveHTML provides a mechanism for embedding non-Oracle information into an Oracle Web page. Oracle has implemented the concept of Server Side Includes (SSI) into its WebServer architecture through the LiveHTML constructs and the LiveHTML Interpreter. SSI enables the creation of dynamic Web documents through various methods, including: • • • • •<br />
<br />
Embedding other LiveHTML documents into Web pages Embedding static Web pages Referencing system variables Executing a script on the server, which produces HTML Executing PL/SQL procedures using CGI<br />
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Oracle Databases on the Web:Using Java And LiveHTML With Oracle WebServer<br />
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To embed LiveHTML within Web pages, LiveHTML must be parsed by the Oracle WebServer, which is not a requirement for normal HTML documents. LiveHTML is syntactically the same as SGML, so, unless the code is parsed, it will not be processed by the browser. In Figure 12.3, you can see the Web Request Broker Administration screen, where you can click on the hyperlink to modify the WRB configuration for the Oracle Web Listener processing the LiveHTML request. Clicking on the hyperlink will transfer you to the Web page shown in Figure 12.4, which is used for modifying the SSI cartridge (LiveHTML Interpreter). Figure 12.5 shows the settings changed to TRUE for the cartridge parameter ParseHTMLExtn; clicking on the button for Modify Cartridge Configuration will complete the configuration.<br />
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Figure 12.3 The Web Request Broker Administration page.<br />
<br />
Figure 12.4 Modifying the SSI Cartridge configuration.<br />
<br />
Figure 12.5 Setting the SSI parameter ParseHTMLExtn.<br />
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LiveHTML Syntax As mentioned earlier, LiveHTML code is similar to SGML, so the constructs of this language may be familiar to you. LiveHTML code is based on the following syntax: <!--#command arg1="value1" arg2="value2"--> The commands and their arguments are explained as follows: • config—This command defines how the LiveHTML code will be parsed. The arguments related to this command include: • errmsg—This argument allows for the specification of an error message encountered during parsing. • sizefmt—When displaying a file size, this argument will determine the format that will be used. The options include abbrev, which presents the size in kilobytes or megabytes, and bytes, which obviously presents the size in bytes. • timefmt—If any dates are displayed on a LiveHTML document, this argument defines their formatting, based on the strftime library calls of Unix. • cmdech—Passing the value ON through this argument will include output from a non-CGI script into an HTML page. Passing the value OFF (which is the default) will not incorporate the output into the document. • cmdprefix—This argument passes text that is attached to the front of<br />
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all lines of output. • cmdpostfix—The text passed through this argument is attached to the end of every output line. • include—This command allows for a file containing information to be embedded into a Web page. These files can be of different varieties, including normal HTML files, other LiveHTML files, and ASCII files. The arguments related to this command include: • file—This argument specifies the directory name for the file location, relative to the current directory. • virtual—The virtual directory location of the file to be sourced can be specified with this argument. The mapping of virtual directories within Oracle WebServer is accomplished through the WebServer Manager, as discussed in detail in Chapter 4, Installing And Configuring Oracle WebServer. • echo—This command returns the contents of any environmental variables that may be LiveHTML extensions (Server Side Include variables) or CGI environmental variables. From previous chapters, you know that CGI variables are passed between Oracle WebServer and the browser through environmental variables, regardless of whether the gateway interface used is the CGI or Web Request Broker. The argument related to this command is: • 22 var—This argument is required for the echo command and may contain one of the following LiveHTML variables: • Last_Modified—The date (formatted by the config timefmt command) that the file was last updated. • Document_Name—The name of the file currently in process. • Document_URL—The location of the file to be sourced, as specified through a virtual directory. • Date_GMT—The current date and local time zone in Greenwich mean time. GMT is the default time zone for the processing of cookies by Oracle WebServer and can be adjusted within the WebServer applications through the owa_init package discussed in Chapter 8, WebServer’s OWA Utilities. • Date_Local—The current date and local time zone, defined by the most recent config timefmt command. • Query_String_Unescaped—This environment variable contains the string sent by a client in unescaped format, but with special characters escaped with a ‘\’ (backslash). • fsize—This command produces the file size as indicated by the last processed config sizefmt command. The same arguments apply as for the include command. • flastmod—This command produces the date that the file was last updated as formatted by the config timefmt command most recently processed. The arguments for this command are the same as those for the include command. • exec—This command executes a script on the server file system, which may or may not be a CGI script. The arguments related to this command include: • cmd—This argument enables the execution of a non-CGI script on the server by specifying the full directory-path location of the script and possibly using the variables specified by the echo command. The config cmdecho command most recently processed determines whether the output from the non-CGI script will be posted to the Web page. • cgi—This argument enables the specification of the virtual directory<br />
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for a CGI script to be processed on the server. CGI scripts are widely used throughout the Web, but product extensions within Oracle WebServer like LiveHTML are replacing the previously standard processes with improved functionality.<br />
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Examples Of LiveHTML In order to appreciate the power of LiveHTML, let’s take a look at an Oracle application that actually uses LiveHTML. In our example, we start by displaying a Web page that can be used to interrogate Unix environmental information. (See Figure 12.6). Here, we see that the Web page displays a series of hypertext links to perform different functions on the host server. This would be a very common application of LiveHTML because the goal of this application is to issue a Unix host command, capture the output of the command in a Unix flat file, and then display the contents of the flat file on the Web page.<br />
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Figure 12.6 A sample Web page using LiveHTML. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (1 of 7)4/03/2005 6:16:26<br />
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As you can see in Figure 12.6, the Web page allows an Oracle developer to access information about specific characteristics of the Unix server. The Oracle developer can press any of the hypertext links to invoke the LiveHTML embedded in the hypertext links. Listing 12.22 shows the Oracle stored procedure code that generated the Web page in Figure 12.6. Listing 12.22 The Oracle stored procedure for the Unix environment query Web page. create or replace procedure s99 as host_name_in varchar2(20); cursor c1 is select host_name from host order by host_name; host_rec c1%ROWTYPE; BEGIN htp.htmlOpen; htp.headOpen; htp.title('s00'); htp.preOpen; htp.header(1,' htp.header(1,' htp.headClose; htp.preClose;<br />
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Oracle Information Database'); Online Oracle Report Menu','C');<br />
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htp.bodyOpen; htp.formOpen(owa_util.get_owa_service_path || 's99'); htp.FormHidden('host_name_in', host_name_in); file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (2 of 7)4/03/2005 6:16:26<br />
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htp.FormSelectOpen('host_name_in','Choose the Host:'); open c1; loop fetch c1 into host_rec; EXIT WHEN c1%NOTFOUND; htp.formSelectOption(host_rec.host_name); end loop; close c1; htp.formSelectClose; htp.header(2,'Unix Environmental Reports','C'); htp.anchor('http://hostname.com:8888/ssi/tnsnames.html', '<h3>tnsnames.ora file.</h3>'); htp.anchor('http://hostname.com:8888/ssi/df.html', '<h3>File system information. (df -k)</h3>'); htp.FormClose; htp.bodyClose; htp.htmlClose; end; / show errors Now, let’s take a closer look at how this Web page functions. The first option is designed to take a look at the Unix file system on the Unix server and then display the tnsnames.ora file information on the Web page. The second option issues a Unix df -k command and pipes the output into a flat file. What’s happening to cause this listing? Let’s begin by examining the following hypertext link: file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (3 of 7)4/03/2005 6:16:26<br />
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htp.anchor('http://hostname.com:8888/ssi/tnsnames.html', '<h3>tnsnames.ora file.</h3>'); This hypertext link specifies that WebServer is to execute a procedure called tnsnames.html, located in the ssi directory, as specified in the WebServer directory mapping administration page. Listing 12.23 shows the contents of the tnsnames. html HTML document. Listing 12.23 An HTML document with LiveHTML. <HTML> <HEAD> <TITLE>LiveHTML (Server Side Includes) Example</TITLE> <!-- Changed by: Bob Papaj, 14-Nov-1996 --> </HEAD> <BODY> <URL-minder-ignore> <A NAME="TopOfPage" rel="nofollow"></A> </FONT> </P> </URL-minder-ignore> <PRE> <!--#exec cmd="/u99/dba/oracle/app/oracle/product/7.3.2/ows2/sample/ssi/ tnsnames.csh"--> <!--#include file="test1.out"--> </PRE> </BODY> </HTML> In Listing 12.23, you can see some LiveHTML. First, you can see the execution of a C shell script called tnsnames.csh. Listing 12.24 shows the contents of this script. Listing 12.24 C shell script to display tnsnames.ora file. #!/bin/csh file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (4 of 7)4/03/2005 6:16:26<br />
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unalias rm rm *.out echo 'date' > /u99/dba/oracle/app/oracle/product/7.3.2/ows2/sample/ssi/ test1.out cat /etc/tnsnames.ora >> /u99/dba/oracle/app/oracle/product/7.3.2/ows2/sample/ssi/ test1.out Here we see the execution of several Unix commands. The first step deletes all *.out files on the Unix directory. The next command executes the Unix echo command to move the current date into a file called test1.out. Finally, the Unix cat command is used to append the tnanames.ora file after the data in the test1.out file. Now that the desired data has been written to the test1.out file, how does it make its way onto the Web page? Take a close look at the code in Listing 12.23. You should see the following: <!--#include<br />
<br />
file="test1.out"--><br />
<br />
This will take the listing and format it into a Web page for display on your browser. Figure 12.7 shows the output of this procedure.<br />
<br />
Figure 12.7 Sample output listing with LiveHTML. To complete the picture, let’s take a look at Listing 12.25, which shows the HTML code generated to display the contents of the tnsnames.ora file. Listing 12.26 shows the actual contents of this file. Listing 12.25 HTML code for displaying a file on the host. <HTML> <HEAD> file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (5 of 7)4/03/2005 6:16:26<br />
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<TITLE>LiveHTML (Server Side Includes) Example</TITLE> <!— Changed by: Bob Papaj, 14-Nov-1996 --> </HEAD> <BODY> <URL-minder-ignore> <A NAME="TopOfPage" rel="nofollow"></A> </FONT> </P> </URL-minder-ignore> <PRE> <!--#exec cmd="/u01/dba/oracle/app/oracle/product/7.3.2./ows2/sample/ssi/tnsname> <!--#include file="test1.out"--> </PRE> </body> </html> Listing 12.26 Contents of tnsnames.ora file. Wed Dec 11 10:29:23 EST 1996 ################ # Filename......: tnsnames.ora # Node..........: joey.world # Date..........: 26-Aug-96 01:00:24 ################ howard = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (COMMUNITY = TCPCOMM) (PROTOCOL = TCP) (Host = sandbox) (Port = 1600) ) ) file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch12/423-430.html (6 of 7)4/03/2005 6:16:26<br />
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(CONNECT_DATA = (SID = DBAP) ) ) william = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (COMMUNITY = TCPCOMM) (PROTOCOL = TCP) (Host = sandbox) (Port = 1600) ) ) Here, you can see that the spooled output listing from the C shell script has been tagged for HTML display. This should complete the picture of how LiveHTML can be used to include Unix files and execute Unix scripts on a server.<br />
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Summary Now that we have looked at the usage for Java and LiveHTML in a WebServer environment, we can move on to the performance and tuning of the Oracle server. Regardless of how well you have tuned your WebServer engine, the bulk of the application work will still be done within the Oracle database. With the Oracle database becoming your weakest link, the following chapters are dedicated to improving the performance of the Oracle engine with an eye toward creating fast and efficient WebServer applications.<br />
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Oracle Databases on the Web:Using SQL*Net For WebServer Communication<br />
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CHAPTER 13 Using SQL*Net For WebServer Communication In a WebServer application, it is unusual for all of the databases to be on the same host as the WebServer engine. Rather, we expect to see Oracle databases distributed onto other host computers and Oracle’s SQL*Net used as the backbone for communications. Distributed Oracle systems enable load-balancing of the subsets of an application, giving each subset of data its own dedicated CPU. In a fully distributed Oracle environment, the WebServer exists as a standalone application on one server while the Oracle databases exist on remote servers. Whenever you have this type of distributed Oracle architecture, you must carefully examine the connectivity issues, so WebServer developers will be able to process data from all of the Oracle servers, regardless of their physical location. This requires a good understanding of SQL*Net, database links, table replication techniques, and distributed Oracle design. This chapter should give you a conceptual understanding of the role of SQL*Net and how it fits into the overall WebServer architecture.<br />
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Location Transparency And WebServer Connectivity Location transparency refers to the ability of a distributed database to function as a unified whole, appearing to developers as a single, unified Oracle database. Where the database resides, what type of database is used, or the required database access methods are all unimportant to end users, and a good design can greatly enhance the file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/431-434.html (1 of 3)4/03/2005 6:16:27<br />
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Oracle Databases on the Web:Using SQL*Net For WebServer Communication<br />
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creation of WebServer applications. To understand location transparency, let’s assume that we have a parts inventory system with separate databases in San Francisco, New York, and Chicago. Let’s also assume that this is a horizontally partitioned database with inventory tables at each location. (A horizontal partition is a very large table that is split into smaller tables, each with the remote site’s data.) Because of this partitioning of the INVENTORY table, it is impossible to directly issue a single SQL command to get the contents from the INVENTORY table at all three locations. However, through the magic of SQL*Net, it’s possible to make remote tables appear as single unified tables. So, if a manager wishes to know the number of widgets on hand in all locations, she could issue the following SQL command to the distributed database manager: select count(*) from INVENTORY where partname = 'widget'; Because we have implemented data location transparency with SQL*Net, the end user does not know or care what databases are interrogated to satisfy his request. In the previous example of count(*) with location transparency, the end user has no interest in any individual databases when servicing the request, defining it as a global transaction. The transaction manager has the responsibility to query all of the distributed INVENTORY tables and collect the counts from each table, merging them into a single result set. In Oracle with SQL*Net, creating database links to the remote database and assigning a global synonym to the remote tables achieves location transparency. At the lowest level, computers are identified by an Internet Protocol (IP) address, which gives the computer a distinct number. An example would be 222.223.90.27. The IP address is associated with a server name using a Unix file called hosts. Table 13.1 shows how these items are associated within an Oracle environment. Table 13.1Associating database names and Unix addresses. Item<br />
<br />
Unix Location<br />
<br />
Example<br />
<br />
Definition<br />
<br />
Telnet<br />
<br />
/etc/hosts<br />
<br />
jason<br />
<br />
Associates IP addresses with Telnet names<br />
<br />
Database<br />
<br />
/etc/oratab<br />
<br />
custserv<br />
<br />
Lists the Oracle system IDs<br />
<br />
TNS Service<br />
<br />
/etc/tnsnames.ora<br />
<br />
custserv<br />
<br />
Defines a protocol, server, and database<br />
<br />
The three files—hosts, oratab, and tnsnames.ora—provide Oracle with the necessary information to uniquely identify each distributed database. In databases such as Oracle with SQL*Net, transparency is achieved by creating database links to remote databases and then assigning a global synonym to the fully qualified table name. Database links are created in Oracle by specifying three items: name of the database link, transparent network substrate (TNS) service name for the remote database (as defined in the SQL*Net tnsnames.ora file), and name of the Oracle user ID initiating the transaction on the remote server. Transparent network substrate is a fancy term for a single, common interface to all protocols that enables<br />
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end users to connect to databases in physically separate networks. At the lowest level, TNS communicates to other databases with message-level send/receive commands. In the following example, omaha.com is the database link, and it connects to the omaha_server TNS service using the oracle_user_profile user ID: create public database link omaha.com connect to omaha_server using oracle_user_profile; Now that we have defined the location name, we can include tables from any of the omaha sites by qualifying the remote site name in the SQL query. In the following example, we join the EMPLOYEE table in omaha with our local SKILLS table: select<br />
<br />
EMPLOYEE.employee_name, SKILLS.skills_date from EMPLOYEE@omaha.com, SKILLS where EMPLOYEE.emp_number = SKILLS.employee_number order by skills_date<br />
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But how do we hide the fact that the EMPLOYEE table resides in omaha? To make the location of this table transparent to the developer, the DBA may assign synonyms for the EMPLOYEE table in omaha that would make the query appear to be a local table: create synonym EMPLOYEE for EMPLOYEE@omaha; The query can now be run with full location transparency: select from<br />
<br />
EMPLOYEE.employee_name, SKILLS.skills_date EMPLOYEE, SKILLS<br />
<br />
where EMPLOYEE.emp_number = SKILLS.employee_number order by skills_date ;<br />
<br />
Note: It is important to understand which Oracle instances are servicing this request. Obviously, the omaha instance is responsible for retrieving the EMPLOYEE rows, but it is not so apparent that it’s the initiating instance’s job to perform the merge sort for the join. The local instance will also be the server that will sort the result set by skills_date. Therefore, if you are issuing this type of distributed request from a WebServer host, you need to ensure that your local WebServer database has enough space in the temporary tablespace and that the sort_area_size init.ora parameter is large enough to handle the sorting operations.<br />
<br />
Oracle stored procedures can also be defined to allow for location transparency. Because the exact table name and TNS location is hidden inside the stored procedure, the developer who calls the file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/434-438.html (1 of 4)4/03/2005 6:16:28<br />
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routine can access the remote table without any reference to its physical location. For example, the following procedure could be defined to allow updates to the EMPLOYEE table in omaha: create procedure add_employee (emp_name char(8)) as begin insert into EMPLOYEE@omaha. values (emp_name); end; This procedure could be called with a single statement: add_employee("Rick Tytler"); Location transparency can be very useful for hiding the complexity of a distributed Oracle system, but there is much more to the story. Oracle Database Domains Most WebServer developers recognize the need to organize and manage remote locations of databases while providing location transparency to key developers. To Oracle, the term domain is used to define each remote database. Domains are especially important in situations of horizontal partitioning. Horizontal partitioning occurs when tables with identical names are kept in numerous locations. Domains can be used within Oracle to establish a logical hierarchy of physical locations for all of the databases that participate in the WebServer application. The sample database shown in Figure 13.1 establishes a domain hierarchy for remote databases.<br />
<br />
Figure 13.1 Example of a WebServer TNS domain model. Each node in the network shown in Figure 13.1 assigns synonyms for all unique tables within the distributed network. For duplicate table structures existing at many locations, abbreviated domains can be created. Assume that both Japan and Ohio have an EMPLOYEE table, identical in structure but containing different rows. We could assign Oracle synonyms as follows: create synonym japan_employee for create synonym ohio_employee for<br />
<br />
EMPLOYEE@hq.sales.asia.japan; EMPLOYEE@hq.mtfg.ohio;<br />
<br />
Intersystem Connectivity With WebServer SQL*Net makes it easy to allow cross-database access, so the issue of intersystem connectivity must be understood. In a distributed Oracle system, you may see any of the following types of table partitioning: • Table Replication—Tables are copied to remote locations using Oracle’s snapshot facility. • Vertical Partitioning—Tables are sliced vertically, placing different columns of the same logical table in remote locations. • Horizontal Partitioning—Tables are sliced by row, placing logically related rows in different physical locations. • Functional Partitioning—Different functional tables exist in different remote locations.<br />
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One very common method of Oracle database distribution is to use horizontal partitioning, where different rows exist at remote locations and SQL*Net makes the remote tables appear as a single table. For example, employee service organizations commonly allow their remote sites to maintain employee information and maintain a location-transparent access mode to every employee, regardless of their physical location. Horizontal partitioning is achieved by taking a subset of each remote site’s EMPLOYEE table and populating a master lookup table that is accessible from any node in the distributed system (see Figure 13.2).<br />
<br />
Figure 13.2 Horizontal data partitioning of a master lookup table for a distributed WebServer application. In a WebServer system, the Unix cron utility can be used to schedule a periodic refresh of the master table. cron is short for chronological, and it’s the name of the Unix utility used to schedule jobs. As such, cron is a time-dependent task activation utility that starts tasks at predetermined dates and times. An SQL script would automatically extract employee_name from the remote site and repopulate the master EMPLOYEE table, leaving the employee details at the remote site. The Oracle SQL might look like this: /*<br />
<br />
Delete remote rows in the master table... */<br />
<br />
delete from employee@master where location = :our_site; /*<br />
<br />
Repopulate the master table...<br />
<br />
*/<br />
<br />
select employee_name, ":our_site" from employee@:OUR_SITE as insert into employee@master values employee_name, site_name; Once populated, the master lookup table can be accessed by any node and used to redirect the database query to the appropriate remote database for employee detail (see Figure 13.3).<br />
<br />
Figure 13.3 Example of location transparency for a distributed WebServer application. Because of dynamic substitution in SQL, a common application can be made to access any employee in the federation, regardless of the location and without any coding changes. For a complete description of these techniques, refer to the text Managing Distributed Databases by Donald K. Burleson, published by Wiley-QED Publishing. Now that we understand how to make each location transparent to the WebServer application, let’s explore the internals of Oracle’s SQL*Net. SQL*Net is a powerful tool that allows many different configurations. A good knowledge of SQL*Net and all of its possible configurations will file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/434-438.html (3 of 4)4/03/2005 6:16:28<br />
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Internals Of Oracle’s SQL*Net In its most basic form, SQL*Net is a software tool that enables a network of Oracle clients and servers to communicate transparently on top of any underlying network topology or protocol using SQL. Although SQL*Net is a robust and sophisticated tool, you must appreciate the inherent complexity that goes along with the flexibility of SQL*Net. Due to the sophisticated architecture of SQL*Net, it’s not trivial to install SQL*Net on the WebServer or any of the remote servers. Because we are dealing with a WebServer front end, it’s important to note that the WebServer host will be the client, while the remote Oracle databases will be the servers. For a general overview of the SQL*Net architecture, let’s begin by looking at the control files for SQL*Net. In Unix systems, the following four files are necessary to operate SQL*Net 2.0: • tnsnames.ora—Used for outgoing database requests, this file contains all of the database system identifiers (SIDs) running on the processor, as well as the domain name, protocol, host, and port information. When a new database is added to a server, you must update this file (changes to tnsnames.ora become effective instantly). Note that the SQL*Net version 1.0 equivalent to Oracle’s tnsnames.ora file is the /etc/oratab file. • listener.ora—This file contains a list of local databases for use by incoming connections. When you add a new destination database to a Unix host, you must also add it to this file.<br />
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• hosts—This file lists all of your network addresses. • services—This file lists all of the SQL*Net services. On some flavors of Unix, such as HP-UX, these files are located in the /etc directory. For Solaris Unix, the .ora files are located in the /var/opt/ oracle directory. In SQL*Net version 2.0, Oracle has added several important enhancements. Aside from the badly needed bug fixes, SQL*Net now allows access to multiple communities. A community is a group of computers that share a common communications protocol (such as TCP/IP to LU6.2). In addition, the Oracle7 database engine now allows for the creation of a multithreaded server (MTS) for servicing incoming data requests. In an MTS, all communication to databases is handled through a single dispatcher, rather than a separate process being spawned for each incoming database connection, as is the case with SQL*Net version 1.0. When upgrading from SQL*Net 1.0 to SQL*Net 2.0, you should be aware of subtle differences between how the two versions handle communications. (See Figure 13.4.) SQL*Net version 1.0 uses an orasrv component on the destination database to listen for incoming requests, while SQL*Net 2.0 uses a process called tnslsnr (TNS listener). In addition, SQL*Net 1.0 cannot use an MTS.<br />
<br />
Figure 13.4 A comparison of the two versions of SQL*Net. When a connection is made to SQL*Net, it passes the request to its underlying layer—the TNS—where the request is transmitted to the appropriate server. At the server, SQL*Net receives the request from the TNS and passes the SQL to the database. On the client side, the User Programmatic Interface (UPI) converts SQL to associated parse, execute, and fetch statements. The UPI parses the SQL, opens the SQL cursor, binds the client application, describes the contents of returned data fields, executes the SQL, fetches the rows, and closes the cursor. Oracle attempts to minimize messages to the server by combining UPI calls whenever possible. On the server side, the Oracle Programmatic Interface (OPI) responds to all possible messages from the UPI and returns requests. All of this work is done after the request has been spawned through the Web Listener and the Web Request Broker. Hence, there are many intermediate steps that a WebServer request must perform before actually retrieving the Oracle data. To further complicate matters, no UPI exists for server-to-server communication. Instead, a Network Programmatic Interface (NPI) resides at the initiating server, and the responding server uses its OPI for the request. SQL*Net supports network transparency so that the network structure may be changed without affecting the SQL*Net application. Location transparency is achieved with database links and synonyms.<br />
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Let’s trace a sample WebServer data request through SQL*Net. The following steps are performed: 1. A request is intercepted by the Web Listener, which spawns a process connection to the Web host processor. 2. The request is then passed to the Web Request Broker (WRB), or the Common Gateway Interface (CGI) for WebServer version 1.0. 3. The request is then directed to the SQL*Net listener on the WebServer host. For PL/SQL requests, the stored procedure is then extracted from the WebServer’s local Oracle database. 4. The stored procedure is then interpreted, and all references to remote Oracle databases are resolved. Requests are sent to each of the remote databases, where their SQL*Net listeners intercept and service the requests. 5. The Oracle transaction manager then receives the data from each of the remote requests and performs all necessary sort and merge operations, delivering a single solution set for the SQL request. 6. The solution set is then passed back to the Web Request Broker (or CGI), which, in turn, passes the data back through the Web Listener to the requesting WebServer client. But wait, it gets even more complex. As each data request is processed by the WebServer host, SQL*Net looks for the link name in the database link table (DBA_DB_LINKS) and extracts the service name. The service name is then located in the tnsnames.ora file, and the host name is extracted. Once again, we have a threestage process beginning with the link name referencing the service name, and then the service name referencing the host name.<br />
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In Unix environments, the host name is usually found in a host file (/etc/hosts), and the Internal Protocol (IP) address is gathered. In the following example, omaha_server might translate into an IP address of 143.32.142.3. The following four steps illustrate how SQL*Net takes a remote request and translates it into the IP address of the destination database: 1. Issues a remote request, and checks the database link called omaha. select * from EMPLOYEE@omaha; 2. The database link gets the service name (omaha_server_d) using the link_name (omaha). create public database link omaha connect to omaha_server_d; 3. tnsnames.ora gets the SID name (omaha_sid) using service name (omaha_server_d). omaha_server_d = (description=(address=(protocol=tcp) (host=bluegill) (port=1521) (connect_data=(sid=omaha_sid) (server=dedicated))) 4. /etc/hosts gets the IP address (143.32.142.3) using the SID name (omaha_sid). 143.32.142.3<br />
<br />
omaha_sid<br />
<br />
omaha_server.corporate.com<br />
<br />
As you can see, this translation occurs in a multistage process. The tnsnames.ora file specifies the name of the host containing the destination database. For Unix environments, this host name is then looked up in the /etc/hosts file to get the IP address of the destination box. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/442-445.html (1 of 3)4/03/2005 6:16:29<br />
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Note that the service name is looked up in tnsnames.ora — if the service exists, the IP address is found in the /etc/hosts file, and a communications request is sent to the destination IP address. Both of the entries in this file connect to omaha, but omaha_server_d directs SQL*Net to spawn a dedicated process, while omaha_server uses the multithreaded server component because a shared server is specified. Now that you have the tnsnames.ora and /etc/hosts files in place, you can include any tables from the omaha sites by qualifying the remote site name in the SQL query. select EMPLOYEE.employee_name, SKILLS.skills_date from EMPLOYEE@omaha, SKILLS where EMPLOYEE.emp_number = SKILLS.employee_number; Note that this query joins two tables at different locations, and the database link called omaha determines how the Oracle connection will be established on the destination system. However, regardless of how the connection is made to the destination, the user ID must have select privileges against the EMPLOYEE table, or this query will fail. Application Connection With SQL*Net Connections to remote databases can be made by specifying either the service names or connect strings. For SQL*Net, connect strings use the full connection, specifying the protocol:server: database. In the following example, the t: means a TCP/IP connection, host: is the name of the remote processor, and database: is the name of the databases on the host processor. The format for the two selections are: • Connect via a service name—emp@my_db • Connect via a server connect string—sqlplus /@t:host:database Connect strings are stored in the DBA_DBLINKS table and are created with the create database link command, as follows: create public database link ny_emp for ny_emp@t:myhost:mydatabase; SQL*Net can establish database communications via three methods: remote connection, remote request, or distributed request. A remote connection is the easiest way to make a database connection. The sending database simply makes a request by specifying a table name suffixed by @. SQL*Net takes it from there, seamlessly accessing the remote database and returning the data to the initiating system. Communication is established by making a distributed request to a remote database. Within Oracle, @ specifies the remote database name, but the functionality of the @ operator depends on where it’s used. Here’s an example: sqlplus scott/tiger@omaha select count(*) from EMPLOYEE; count(*) —————— 162 In this request, scott is using SQL*Plus to connect to the omaha database, and @omaha is the service name, as defined in the tnsnames.ora file. SQL*Net recognizes this as a remote connection and determines the appropriate linkage to establish communications with omaha. Internally, Oracle will check the tnsnames.ora file to ensure that omaha is a valid destination. However, there file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/442-445.html (2 of 3)4/03/2005 6:16:29<br />
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is another way of connecting to omaha from the same database. This is called a remote request. Following is an example of a remote request: sqlplus scott/tiger select count(*) from EMPLOYEE@omaha; count(*) ——————— 162 Unlike a remote connection made directly from SQL*Plus, the remote request has scott connecting to the local copy of SQL*Plus to specify the remote table (in this case, EMPLOYEE@omaha). For a remote request to work, a database link must define omaha. A database link is a connection pathway to a remote database that specifies the service name of the remote database. Without the database link, the following request would fail: sqlplus jenny_burleson/secret_password select count(*) from EMPLOYEE@omaha; This request will give you the following error message: ORA-02019: Connection description for remote database not found. This error message results from the way Oracle defines the @ operator for remote connections. When entering an Oracle service, such as SQL*Plus from the Unix command prompt, the @ operator will go directly<br />
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Let’s take a closer look at a database link. In this simple example, no mention is made of the user ID used to establish the connection on the remote database. Because scott is the user connecting to SQL*Plus, scott will be the user ID when the remote connection is established to the omaha database. Therefore, scott must have select privileges against the EMPLOYEE table in omaha in skills for the query to work properly. scott’s privileges on the initiating Oracle database have no bearing on the success of the query.<br />
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Note: If you are using the Oracle Names facility, you must be sure that your database service names are the same as the global_databases_names and the domain init.ora parameter. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/445-448.html (1 of 4)4/03/2005 6:16:30<br />
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In cases where select security is not an issue, you can enhance the database link syntax to include a remote connect description: create database link omaha using 'omaha' connect to SCOTT1 identified by TIGER1; This way, all users who specify the omaha database link will connect as scott1 // and will have whatever privileges scott1 // has on the omaha system. Once you establish a communications pathway to the remote database, it is often desirable to implement location transparency. In relational databases such as Oracle, you can obtain location transparency by creating database links to the remote database and then assigning a global synonym to the remote tables. The database link specifies a link name and an SQL*Net service name. You can create database links with a location suffix that is associated with a host name (in this example, omaha_server). You can use database links to allow applications to point to other databases without altering the application code. For data warehousing applications, you can replicate a table on another machine and establish links to enable the application to point transparently to the new box containing the replicated table. To see the links for a database, query the Oracle dictionary in the following manner: select distinct db_link from DBA_DB_LINKS; Keep in mind that SQL*Net bypasses all operating system security settings when it connects to a database. All user accounts identified externally (that is, without an Oracle password) will not be allowed in SQL*Net transactions unless the init.ora parameter is changed. The identified externally clause (sometimes called OPS$) in Oracle version 6 allowed the operating system to manage passwords, but because SQL*Net bypasses the operating system, impostor accounts could be created from other platforms. For example, a Unix user running a PC-based Unix operating system such as Coherent could set their user ID to anyone they desired, and then connect with SQL*Net to any remote database with all database privileges consistent with the user ID. Consequently, Oracle now recommends that identified externally accounts be forbidden for distributed connections. It is interesting to note that Oracle will allow you to create accounts with an OPS$ prefix. Therefore, the operating system can manage its passwords, while you also have passwords within Oracle. For example, assume the following user definition:<br />
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create user ops$scott identified by tiger; Assuming that scott has logged onto the operating system, scott could enter SQL*Plus either with or without a password, as follows: sqlplus / sqlplus scott/tiger This ability to connect directly to Oracle presents a confounding issue with password management. Because two sets of passwords exist—one in the operating system and another in Oracle—you may need a third-party tool to keep the passwords synchronized. Understanding The SQL*Net Listener Each version of Oracle has its own listener process. For SQL*Net version 1.0, the listener process is called orasrv, and the SQL*Net version 2.0 listener process is called tnslsnr. Using the Unix ps command, you can see the listener processes running on your server, as shown in Listing 13.1. Listing 13.1 A sample Unix ps command. ps -ef|grep ora oracle 1201 1 80 LISTENER -inherit oracle 934 1 3 oracle 1443 1 83 oracle/app/orac oracle 1231 1 80 oracle/app/orac<br />
<br />
Nov 13 0:02<br />
<br />
/u00/oracle/product/7.3.2/bin/tnslsnr<br />
<br />
Nov 13 0:00 Nov 13 0:32<br />
<br />
orasrv /u00/oracle/product/7.3.2/bin/oraweb -C u00/dba/<br />
<br />
Nov 13 0:02<br />
<br />
/u00/oracle/product/7.3.2/bin/wrb2 16 4 /u00/dba/<br />
<br />
From Listing 13.1, we can see the SQL*Net listeners, WebServer listener, and Web Request Broker running on this server. To see what the Oracle listeners are doing, Oracle provides a series of listener commands, which include: • reload—Refreshes the listener • start—Starts the listener file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch13/445-448.html (3 of 4)4/03/2005 6:16:30<br />
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• stop—Stops the listener • status—Shows the status of the listener • services—Shows all connected services for the listener There are three listeners that accept and activate these commands. The activation commands are as follows: • tcpctl—Command to the SQL*Net v 1 Listener • lsnrctl—SQL*Net v 2 Listener • wlctl—Web Listener<br />
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Therefore, if we wanted to check the status of the SQL*Net version 2.0 Listener, we could issue the command lnsrctl stat. Listing 13.2 shows the output of the lsnrctl stat command. Listing 13.2 A sample output from the SQL*Net Listener command. [oracle]ram2: lsnrctl stat LSNRCTL for HPUX: Version 2.0.15.0.0 - Production on 16-SEP-94 15:38:00 Copyright (a)<br />
<br />
Oracle Corporation 1993.<br />
<br />
All rights reserved.<br />
<br />
Connecting to (ADDRESS=(PROTOCOL=TCP)(HOST=ram2)(PORT=1521)) STATUS of the LISTENER ———————————— Alias LISTENER Version TNSLSNR for HPUX: Version 2.0.15.0.0 - Production Start Date 29-AUG-94 13:50:16 Uptime 18 days 1 hr. 47 min. 45 sec Trace Level off Security OFF Listener Parameter File /etc/listener.ora Listener Log File /usr/oracle/network/log/listener.log Services Summary... dev7dba has 1 service handlers ram2dba has 1 service handlers The command completed successfully lsnrctl services<br />
<br />
- lists all servers and dispatchers<br />
<br />
[oracle]bluegill: lsnrctl services LSNRCTL for HPUX: Version 2.0.15.0.0 - Production on 16-SEP-94 15:36:47 Copyright (a)<br />
<br />
Oracle Corporation 1893. All rights reserved.<br />
<br />
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Connecting to (ADDRESS=(PROTOCOL=TCP)(HOST=bluegill)(PORT=1521)) Services Summary... ftdab000 has 4 service handlers DISPATCHER established:1 refused:0 current:2 max:55 state:ready D001 (machine: bluegill, pid: 4146) (ADDRESS=(PROTOCOL=tcp)(DEV=5)(HOST=141.123.224.38)(PORT=1323)) DISPATCHER established:1 refused:0 current:2 max:55 state:ready D000 (machine: bluegill, pid: 4145) (ADDRESS=(PROTOCOL=tcp)(DEV=5)(HOST=141.123.224.38)(PORT=1321)) DISPATCHER established:0 refused:0 current:1 max:55 state:ready D002 (machine: bluegill, pid: 4147) (ADDRESS=(PROTOCOL=tcp)(DEV=5)(HOST=141.123.224.38)(PORT=1325)) DEDICATED SERVER established:0 refused:0 The command completed successfully As a service request is intercepted by an Oracle server, the listener may direct the request via a dedicated server, an MTS, or an existing process (also known as a prespawned shadow). The key is whether the connection contacts the listener via a service name or bypasses the listener with the two_task connect string. If the listener is contacted as part of the connection and the MTS parms are defined to init.ora, the client will use the MTS. There are five basic listener commands: reload, start, stop, status, and services. Based on the request, the listener decides whether to dispatch a connection to a dedicated-server process (which it spawns) or to use the MTS. The programmer has several options when deciding how Oracle will manage the process. Dedicated requests can be specified by a version 1.0 connect string or by using a service name that specifies server=dedicated in the tnsnames.ora file. Managing SQL*Net Connections Listing 13.3 describes some of the utilities you can use to manage SQL*Net sessions effectively. You should be aware that some of the examples in this section are operation system–independent and may not apply to your environment. Listing 13.3 Commit point strength. commit.sql - Reports the commit point strength for the database. set feedback column name column type column value<br />
<br />
off format a30 heading 'Name' format a7 heading 'Type' format a60 heading 'Value'<br />
<br />
prompt Commit Point-strength Report Output: prompt prompt select name, decode(type,1,'boolean', 2,'string', 3,'integer', 4,'file') type, replace(replace(value,'@','%{sid}'),'?','%{home}') value from v$parameter where name = 'commit_point_strength';<br />
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Managing Oracle’s Multithreaded Server One of the problems with SQL*Net version 1.0 was that each incoming transaction was spawned by the listener as a separate operating system task. With SQL*Net version 2.0, Oracle now has a method for allowing the listener connection to dispatch numerous subprocesses. With the MTS, all communications to a database are handled through a single dispatcher instead of separate Unix process IDs (PIDs) on each database. This translates into faster performance for most online tasks. Even local transactions will be directed through the MTS, and you will no longer see a PID for your local task when you issue the Unix command ps -ef|grep oracle. However, be aware that the MTS is not a panacea, especially at times when you want to invoke a dedicated process for certain WebServer connections. For a process that has little idle time, such as an intensive table update with WebServer (and also Pro*C programs or I/Ointensive SQL*Forms applications), you will get better performance if you bypass the MTS and use a dedicated process connection. In general, the MTS offers benefits, such as reduced memory use, fewer processes per user, and automatic load balancing. Remember the following rules of thumb when initially starting the MTS: • The MTS is governed by the init.ora parameters. If no MTS parms are present in init.ora, the MTS is disabled. • The MTS is used when the MTS parms are in the init.ora and requests are made by service name (such as @my_database). In other words, you must retrieve the rowid of all version 1.0 connect strings (such as t:unix1:my_database). • Each user of the MTS requires 1 K of storage, so plan to increase your shared_pool_size.<br />
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• The V$QUEUE and V$DISPATCHER system tables indicate whether the number of MTS dispatchers is too low. Even though the number of dispatchers is specified in the init.ora file, you can change it online in SQL*DBA with the alter system command, as follows: SQLDBA> alter system set mts_dispatchers = 'TCPIP,4'; • If you encounter problems with the MTS, you can quickly regress to dedicated servers by issuing an alter system command. The following command turns off the MTS by setting the number of MTS servers to 0: SQLDBA> alter system set mts_servers=0; • In order to use OPS$, you must set two init.ora values to true (the default is false), as follows: remote_os_authent = true remote_os_roles = true • When both SQL*Net 1.0 and 2.0 are installed, the user may connect to the server via a dedicated server or the MTS. However, you cannot stop and restart the listener when connecting via the MTS. You must connect to SQL*DBA with a dedicated server. • In some cases, the instance must be bounced if the listener is stopped, or it will restart in dedicated mode. Whenever an instance is to be bounced, stop the listener, shut down the instance, restart the listener, and start up the instance. The listener reads the MTS parameters only if it’s running before startup of the instance. Therefore, bouncing the listener will disable the MTS. Managing The Listener Processes The listener is a software program that runs on each remote node and “listens” for any incoming database requests. When a request is detected, the listener may direct the request to any of the following: • Dedicated server • Multithreaded server • Existing process or prespawned shadow Note that the configuration of an Oracle listener is a direct result of the parameters specified in the startup deck for the Oracle database. This parameter file is called init.ora and will contain the parameters used to define the multithreaded server and listener, as shown in Listing 13.4. Listing 13.4 init.ora parameters for the multithreaded server. #———————————# Multithreaded Server #———————————MTS_DISPATCHERS<br />
<br />
= "tcp,3"<br />
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MTS_LISTENER_ADDRESS = "(ADDRESS=(PROTOCOL=tcp) (HOST=bluegill) (PORT=1521))" MTS_MAX_DISPATCHERS<br />
<br />
= 5<br />
<br />
MTS_MAX_SERVERS<br />
<br />
= 20<br />
<br />
#—————————————# Distributed systems options #—————————————DISTRIBUTED_LOCK_TIMEOUT<br />
<br />
= 60<br />
<br />
DISTRIBUTED_RECOVERY_CONNECTION_HOLD_TIME = 200 DISTRIBUTED_TRANSACTIONS<br />
<br />
= 6<br />
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Managing Two-Phase Commits (2PCs) In some cases, you may want your WebServer application to issue updates against two or more remote databases in a single SQL command. When a distributed update (or delete) has finished processing, SQL*Net will coordinate commit processing, which means that the entire transaction will roll back if any portion of the transaction fails. The first phase of this process is to issue a prepare phase to each node, followed by the commit, and then terminated by a forget phase. If a distributed update is in the process of issuing the 2PC and a network connection breaks, Oracle will place an entry in the DBA_2PC_PENDING table. The recovery background process (RECO) will then roll back or commit the good node to match the state of the disconnected node to ensure consistency. You can activate RECO via the alter system enable distributed recovery command. The DBA_2PC_PENDING table contains an advise column that directs the database to either commit or roll back the pending item. You can use the alter session advise syntax to direct the 2PC mechanism. For example, to force the completion of an insert, you could enter the following: alter session advise commit; insert into payroll@omaha. .. ; When a 2PC transaction fails, you can query the DBA_2PC_PENDING table to check the state column. You can enter SQL*DBA and use the Recover In-Doubt Transaction dialog box to force either a rollback or a commit of the pending transaction. If you do this, the row will disappear from DBA_2PC_PENDING after the transaction has been resolved. If you force the transaction the wrong way (for example, rollback when other nodes committed), RECO will detect the problem, set the mixed column to yes, and the row will remain in the DBA_2PC_PENDING table. Internally, Oracle examines the init.ora parameters to determine the rank that the commit processing will take. The commit_point_strength init.ora parameter determines which of the distributed databases is to be the commit point site. In a distributed update, the database with the largest value of commit_point_strength will be the commit point site. The commit point site is the database that must successfully complete before the transaction is updated in the other databases. Conversely, if a transaction fails at the commit point site, the entire transaction will be rolled back at all of the other databases. In general, the commit point site should be the database that contains the most critical data. Listing 13.5 shows a script that identifies 2PC transactions that have failed to complete. Listing 13.5 pending.sql reports on any pending distributed transactions.<br />
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set pagesize 999; set feedback off; set wrap on; column local_tran_id column global_tran_id column state column mixed column advice select from skills<br />
<br />
format format format format format<br />
<br />
a22 a50 a16 a5 a5<br />
<br />
heading heading heading heading heading<br />
<br />
'Local Txn Id' 'Global Txn Id' 'State' 'Mixed' 'Advice'<br />
<br />
local_tran_id,global_tran_id,state,mixed,advice dba_2pc_pending by local_tran_id;<br />
<br />
Viewing SQL*Net Sessions On systems running SQL*Net version 2.0, the following SQL*Plus script can be used to query the number of dedicated and shared servers on the system. For example, Listing 13.6 shows an SQL*Plus script to view all sessions. Listing 13.6 session.sql displays all connected sessions. set echo off; set termout on; set linesize 80; set pagesize 60; set newpage 0; ttitle "dbname Database|UNIX/Oracle Sessions"; spool /tmp/session set heading off; select 'Sessions on database '||substr(name,1,8) from v$database; set heading on; select substr(b.serial#,1,5) ser#, substr(b.machine,1,6) box, substr(b.username,1,10) username, substr(b.osuser,1,8) os_user, substr(b.program,1,30) program from v$session b, v$process a where b.paddr = a.addr and type='USER' skills by spid; ttitle off; set heading off; select 'To kill, enter SQLPLUS> ALTER SYSTEM KILL SESSION', ''''||'SID, SER#'||''''||';' from dual; spool off; [oracle]ram2: sqlx session Wed Sep 24 Page 1 ram2db Database Sessions for SQL*Net SERVER<br />
<br />
Oracle user<br />
<br />
——————<br />
<br />
——————————<br />
<br />
O/S<br />
<br />
User<br />
<br />
Machine Program<br />
<br />
————<br />
<br />
————<br />
<br />
—————————————<br />
<br />
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<br />
DEDICATED<br />
<br />
JAME_GASTON<br />
<br />
jgaston<br />
<br />
ram2<br />
<br />
sqldba@ram2 (Pipe Two-Task)<br />
<br />
DEDICATED<br />
<br />
LINDA_ODELL<br />
<br />
lodell<br />
<br />
ram2<br />
<br />
runform30@ram2 (Pipe TwoTask)<br />
<br />
DEDICATED<br />
<br />
RICK_WAHL<br />
<br />
rwahl<br />
<br />
ram2<br />
<br />
sqlplus@ram2 (Pipe Two-Task)<br />
<br />
DEDICATED<br />
<br />
MARK_REULBACH<br />
<br />
mreulbach<br />
<br />
dlt2<br />
<br />
sqlplus@clt2 (TNS interface)<br />
<br />
DEDICATED<br />
<br />
BOB_PAPAJ<br />
<br />
bpapaj<br />
<br />
ram2<br />
<br />
?<br />
<br />
DEDICATED<br />
<br />
DEB_SCHUMACHER dschumacher ram2<br />
<br />
runmenu50@ram2 (Pipe TwoTask)<br />
<br />
DEDICATED<br />
<br />
KAREN_CHAN<br />
<br />
kchan<br />
<br />
sqlplus@ensc (TCP Two-Task)<br />
<br />
DEDICATED<br />
<br />
MARC_MASCARO<br />
<br />
mmascaro<br />
<br />
DEDICATED<br />
<br />
KELVIN_CONNOR<br />
<br />
kconnor<br />
<br />
ram2<br />
<br />
sqlplus@ram2 (Pipe Two-Task)<br />
<br />
DEDICATED<br />
<br />
STEVE_WOHL<br />
<br />
swohl<br />
<br />
ram2<br />
<br />
sqlforms30@ram2 (Pipe TwoTask)<br />
<br />
DEDICATED<br />
<br />
CRISTAL_WONG<br />
<br />
cwong<br />
<br />
ram2<br />
<br />
RUN_USEX@ram2 (Pipe TwoTask)<br />
<br />
xnsc<br />
<br />
@ram2 (TCP Two-Task)<br />
<br />
C:\PB3\PBSYS030.DLL<br />
<br />
11 rows selected. Here we see each of the four types of SQL*Net connections: • Pipe Two-Task—Used for internal tasks (SQLPLUS /). • TNS Interface—Used when a connection is made with a v2 service name (SQLPLUS /@ram2). • TCP Two-Task—Used when a connection is made with a v1 connect string (SQLPLUS /@t: ram2:ram2db). • PC Connection Task—Denoted by the PC DLL name (c:\pb3\pbsys030.dll, which was initiated via PowerBuilder DLL).<br />
<br />
Summary Now that we have reviewed the basics of distributed Oracle database management, you should have a good idea of how a distributed Oracle database can be integrated for use by a WebServer application by using database links and SQL*Net connections. While we can only gloss over the high points of SQL*Net in this chapter, sophisticated tools such as SQL*Net 2.0 require a great deal of knowledge and skill to use effectively. As systems continue to evolve into complex distributed networks, interdatabase communications will continue to become more complex and require more sophisticated tools. Objectorientation promises to make interdatabase communications simple, but the DBA in the trenches will continue to struggle with implementing everyday distributed database communications. In the following chapters, we will take a look at Oracle database design issues to ensure that the Oracle database portion of the WebServer application does not become the bottleneck in the overall system.<br />
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CHAPTER 14 Logical Design For WebServer Applications There are many books containing tips on the effective design of Oracle systems, but many of these texts are purely theoretical and fail to take into account the real-world issues involved in designing a high-performance Oracle database. In this chapter, we’ll take a real-world approach toward designing WebServer applications and discuss the importance of system response time.<br />
<br />
Normalization And Modeling Theory For Oracle As we know, there are five basic types of data relationships that must be modeled when designing any Oracle database: • • • • •<br />
<br />
one-to-one one-to-many many-to-many recursive many-to-many “is a” (ISA)<br />
<br />
The effective WebServer designer must be able to represent these five types of data relationships in a sensible way, while ensuring acceptable Oracle database performance. This chapter focuses on one-to-many and many-to-many relationships. Redundancy And Database Design An Oracle database with either one-to-many or many-to-many relationships has file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/457-460.html (1 of 3)4/03/2005 6:16:32<br />
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redundant foreign keys embedded in the tables to establish logical relationships between entities. The redundant duplication of foreign keys in subordinate tables creates the data relationships, making it possible to join tables together and relate the contents of the data items in the tables. As the size of the database increases, data redundancy can become a major problem. Today, many users create very large databases, many of which contain trillions of bytes. For databases of this size, a single table can contain more than a billion rows, and the introduction of a single new column to a table could represent thousands of dollars in additional disk expense. Data redundancy is detrimental for two reasons. First and foremost, duplicating the redundant material consumes disk storage space. Second, updating redundant data requires extra processing. Redundant duplication of very large and highly volatile data items can cause huge processing bottlenecks. However, this does not imply that redundancy is always undesirable. Performance is still an overriding factor in most systems. Proper control of redundant information implies that redundant information may be introduced into any structure, as long as the performance improvements outweigh the additional disk costs and update problems. Since the first publication of Dr. E. F. Codd’s 1993 research paper, Providing OLAP (Online Analytical Processing) to User-Analysts: An IT Mandate, database designers have attempted to find an optimum way of structuring tables for low data redundancy. Codd’s rules of normalization often guide designers to create logically correct table structures with no redundancy, but many designers have found that performance demands often dictate the introduction of duplicate table data. This is especially true for distributed Oracle databases. Any node in a distributed database may want to browse a list of customers from another node without establishing a connection to it. In addition, the technological complexity inherent in Oracle’s two-phase commit often necessitates the widespread replication of entire tables or selected columns from tables. However, the distributed database designer does not have free reign to introduce redundancy anywhere in the enterprise. Redundancy always has a price tag, whether it is the cost of the disk storage or the cost of maintaining a parallel update scheme. Figure 14.1 shows a strategy for analyzing the consequences of data redundancy.<br />
<br />
Figure 14.1 A comparison of size versus volatility for redundant data. In Figure 14.1, a boundary line lies within a range between the size of a redundant data item and the frequency in which the data item updates. The size of the data item relates to the disk costs associated with storing the item, and the frequency of update is associated with the cost of keeping the redundant data current, whether by replication techniques or by two-phase commit updates. Because the relative costs are different for each hardware configuration and for each application, this boundary may be quite different depending on the type of application. The rapid decrease in disk storage costs<br />
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means that the size boundary is only important for very large-scale redundancy. A large, frequently changing item (for example, street_address) is not a good candidate for redundancy. But large static items (for example, service_history) or small, frequently changing items (such as product_price) may be acceptable for redundancy. Small static items (for example, gender) represent ideal candidates for redundant duplication.<br />
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One-To-Many Data Relationships One-to-many relationships exist in many real-world situations. Many entities that possess one-to-many relationships can be removed from the data model, eliminating some join operations. The basic principle here is simple: Redundant information avoids expensive SQL joins and yields faster processing. But remember, we must deal with the issue of additional disk storage and the problems associated with updating the redundant data. For example, consider the Entity/Relation (E/R) model shown in Figure 14.2.<br />
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Figure 14.2 A fully normalized E/R model sales database. In Figure 14.2, we see that the structure is in pure Third Normal Form. Notice that the CITY and STATE tables exist because each state has many cities and each city has many customers. This model works for most transactions in an online transaction processing (OLTP) system. However, this high degree of normalization would require the joining of the CITY and STATE tables each time address information is requested, forcing some SQL requests to perform very slowly. Consider a query to display the state_bird for all orders that have been placed for birdseed. This is a cumbersome query that requires the joining of six tables, as shown in Listing 14.1. Listing 14.1 Joining six tables. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/460-464.html (1 of 4)4/03/2005 6:16:33<br />
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select state_bird from STATE, CITY, CUSTOMER, ORDER, QUANTITY, ITEM where item_name = 'BIRDSEED' and ITEM.item.nbr = QUANTITY.item.nbr AND QUANTITY.order_nbr = ORDER.order_nbr AND ORDER.cust_nbr = CUSTOMER.cust_nbr AND CUSTOMER.cust_city = CITY.cust_city AND CITY.state_name = STATE.state_name; With Oracle and the rule-based optimizer, this type of complex join guarantees that at least one table is read front to back using a full-table scan, and a full-table scan may slow down even the best WebServer application. This is a shortcoming of Oracle’s rule-based optimizer, because an SQL optimizer should generally avoid a full-table scan whenever indexes are present (except, of course, when the table is very small). This situation might be avoided by using Oracle hints with the cost-based optimizer to determine the optimal path to this data. A hint is an extension of Oracle’s SQL that directs the SQL optimizer to change its normal access path. But what happens if you are designing a data warehouse and your goal is to simplify the data structure by removing several of the one-to-many relationships? For example, you may choose to eliminate the “one” side of a relationship by copying the data columns into the “many” side of the relationship. This is a very common approach in the design of denormalized STAR schemas for use by Oracle 7.3 data warehouses. (We’ll talk more about STAR schemas later in this chapter.) However, adding redundancy poses two issues. First, you need additional disk space for the redundant item, and second, you need to provide a technique to update the redundant item if it needs to be changed. In our example, one solution is to build a table of columns that rolls the CITY and STATE tables into the CUSTOMER table. Table 14.1 assumes that the STATE table contains 50 rows, the CITY table has 2,000 rows, and the CUSTOMER table has 10,000 rows. Table 14.1Redundancy matrix to determine optimal normalization. Column<br />
<br />
Size<br />
<br />
Duplication<br />
<br />
Total Space<br />
<br />
Change<br />
<br />
state_bird<br />
<br />
10<br />
<br />
10,000<br />
<br />
100,000<br />
<br />
Rare<br />
<br />
state_flower<br />
<br />
10<br />
<br />
10,000<br />
<br />
100,000<br />
<br />
Rare<br />
<br />
region_name<br />
<br />
2<br />
<br />
10,000<br />
<br />
20,000<br />
<br />
Never<br />
<br />
cost_of_living<br />
<br />
8<br />
<br />
10,000<br />
<br />
80,000<br />
<br />
Quarterly<br />
<br />
10<br />
<br />
10,000<br />
<br />
100,000<br />
<br />
city_mascot<br />
<br />
Rare<br />
<br />
From Table 14.1, you can see that the CITY and STATE tables can be removed file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/460-464.html (2 of 4)4/03/2005 6:16:33<br />
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entirely for a total savings of 400,000 bytes (refer to Figure 14.3). What about the cost_of_living field? If we choose to eliminate the CITY table, and duplicate cost_of_living in every CUSTOMER table row, it would be necessary to visit each and every CUSTOMER row—which means changing the cost of living 10,000 times. Before this change, the following SQL was used to update each CITY table: update CITY set cost_of_living = :var1 where CITY = :var2; 2000 rows updated<br />
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Figure 14.3 A denormalized E/R model sales database. While the management of redundancy seems a formidable challenge, the following SQL update statement makes this change easily, and we can make the change to all affected rows: update CUSTOMER set cost_of_living = :var1 where CITY = :var2; 100,000 rows updated Using the same state_bird query as before, we see how it is simplified by removing the extra tables, as follows: select state_bird from CUSTOMER, ORDER, QUANTITY, ITEM where item_name = 'BIRDSEED' and ITEM.item_nbr = QUANTITY.item_nbr and QUANTITY.order_nbr = ORDER.order_nbr and ORDER.cust_nbr = CUSTOMER.cust_nbr; It is still necessary to join three tables, but this results in a much faster, simpler query than the original six-way table join. You can carry this concept to the point where this model is condensed into a single, highly redundant table. When creating an E/R model, it is often tempting to look at the data model from a purely logical perspective without any regard for the physical implications of the model. The designer strives to recognize and establish all of the logical relationships in the model while sometimes finding that the relationships are misleading. A relationship can be misleading when the relationship actually exists, but the application may have no need to reference this relationship. Consider the E/R model for a university shown in Figure 14.4. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/460-464.html (3 of 4)4/03/2005 6:16:33<br />
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Figure 14.4 An example of misleading data relationships. Consider the association of the hair_color attribute to the student entity. Does a manyto-many data relationship really exist between hair_color and student? Many students have blonde hair, and blonde hair is common to many students. Why not create a many-to-many relationship between student and hair_color? The solution depends upon whether any other non-key data items exist within the hair_color entity.<br />
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If many other data items relating to hair color are present, then it is perfectly appropriate to create another entity called hair_color. But in this case, even though a many-to-many relationship exists between hair_color and student, hair_color is a standalone data attribute, so it is unnecessary to create an additional data structure. Another example is the zip_code attribute in the student entity. At first glance, it appears that a violation of Third Normal Form (that is, a transitive dependency) has occurred between city and zip_code. In other words, it appears that a zip_code is paired with the city of residence for the student. If each city has many zip_codes, while each zip_code refers only to one city, it makes sense to model this as a one-tomany data relationship (see Figure 14.5). The presence of this data relationship requires creating a separate entity called zip with attached student entities. However, this is another case where the zip entity lacks key attributes, making it impractical to create. In other words, zip_code has no associated data items. Creating a database table with only one data column would be nonsense.<br />
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Figure 14.5 An example of correct many-to-many relationships. The example in Figure 14.5 demonstrates that it is not enough to group together like items and then identify the data relationships. A practical test must be made regarding the presence of no-key attributes within an entity class. If an entity has no attributes file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/464-468.html (1 of 4)4/03/2005 6:16:34<br />
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(that is, the table has only one field), the presence of the entity is nothing more than an index to the foreign key in the member entity. It can be removed from the E/R model. This technique not only simplifies the number of entities, but it creates a better environment for a client/server architecture. More data is logically grouped together, resulting in less data access effort. Many-To-Many Data Relationships Oftentimes, a many-to-many relationship can be condensed into a more efficient structure to improve the speed of data retrieval. After all, with denormalization, less tables will need to be joined together to get the desired information. For example, Figure 14.6 shows how a many-to-many relationship can be collapsed into a more compact structure by considering the relationship between a course and a student.<br />
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Figure 14.6 An example of a university database. A student takes many courses, and each course has many students. This is a classic many-to-many relationship that would require that we define a junction table between the base entities to establish the foreign keys necessary to join the tables together. Note that the junction table is called GRADE with the following contents: • course_nbr—the primary key for the COURSE table • student_nbr—the primary key for the STUDENT table • grade—a no-key attribute to both foreign keys Next, consider the question, In what context does a grade have meaning? Stating that “The grade was A in CS-101” is insufficient, and stating that “Joe earned an A” makes no sense. Only when both the student name and the course number are associated does the grade column have meaning. Stating that “Joe earned an A in CS-101” makes sense. Recursive Data Relationships Recursive many-to-many relationships contain an object that also has a many-to-many relationship with other occurrences of the same object. These relationships are often termed Bill-of-Materials (BOM) relationships, and the graphical representation of the recursive relationship is sometimes termed a Bill-of-Materials explosion. BOM relationships are termed recursive because a single query makes many subpasses through the tables to arrive at the solution (see Figure 14.7).<br />
<br />
Figure 14.7 An example of recursive many-to-many relationships. Bill-of-Materials relationships denote an object with a many-to-many relationship with another object in the same class. For example, a part may consist of other parts, but, at file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/464-468.html (2 of 4)4/03/2005 6:16:34<br />
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the same time, it is a component in a larger assembly. Or, a class at a university may have many prerequisites, but, at the same time, it is a prerequisite for other classes. Bill-of-Materials relationships become even more complex when we begin to create class hierarchies on top of the relationship. In Figure 14.8, you can see that the recursive relationship between parts and components has been extended to allow for different classes of parts, each with its own data elements and behaviors. Unfortunately, these types of challenges are very common. While it is true that “parts are parts,” different parts often have subtle variations—which, of course, leads to separate data columns. For example, a food-related part might have a shelf_life column, but that column does not apply to a non-food part.<br />
<br />
Figure 14.8 Recursive many-to-many relationships with the addition of an ISA hierarchy. With an understanding of the nature of recursive relationships, the question becomes one of implementation: What is the best way to represent a recursive relationship in Oracle and navigate the structure? Listing 14.2 shows Oracle table definitions that describe the tables for our part-component example. Listing 14.2 Oracle table definitions. create table part_nbr part_name part_desc qty_on_hand<br />
<br />
PART( number, varchar2(10), varchar2(10), number);<br />
<br />
create table has_part is_a_part qty<br />
<br />
COMPONENT ( number, number, number);<br />
<br />
Look closely at the COMPONENT example. Both the has_part and is_a_part fields are foreign keys for the part_nbr field in the PART table. Therefore, the COMPONENT table contains all key values except for the qty field, which tells how many parts belong in an assembly. To understand how this works, look at the following SQL code used to display all components in a Big_Meal: select part_name from PART, COMPONENT where has_part = 'BIG MEAL' and PART.part_nbr = COMPONENT.has_part; This type of Oracle SQL query requires joining the table against itself. Unfortunately, file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/464-468.html (3 of 4)4/03/2005 6:16:34<br />
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because all items are of the same type (namely, PART), no real substitute exists for this type of data relationship, therefore the BOM relationship will most likely remain popular in Oracle.<br />
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Using STAR Schema Design With WebServer One of the most popular uses for Oracle WebServer has been servicing the front-end requirements for decision support systems and data warehouses. Oracle has announced that their Oracle Express multidimensional component has now been Web enabled, but there is still a need to use Web pages for the display (and data capture) of decision support information. One common use of WebServer is to allow end users to display highly summarized Oracle data on Web pages, where they can use MS-Windows cut-and-paste commands to extract data into spreadsheets for further analysis. Because the data can be gathered from a Web page, developers do not need to write cumbersome data downloading routines, and end users can get data from anywhere in the world. The STAR schema design was first introduced by Dr. Ralph Kimball as an alternative database design for data warehouses. The name STAR comes from the design that the completed schema creates, where a large fact table resides at the center of the model surrounded by various reference tables, or points. The basic principle behind the STAR query schema is the introduction of highly redundant data for high performance. Returning to the customer-order E/R model in Figure 14.3, we see an illustration of a standard Third Normal Form database used to represent the sales of items. Because redundant information is not an issue, salient data (such as the total for an order) is computed from the items comprising the order. In this Third Normal Form database, users need a list of line items to multiply the quantity ordered by the price for all items belonging in order 123. An intermediate table called TEMP holds the result list, as shown in the following example: create table TEMP as select (QUANTITY.quantity_sold * ITEM.list_price) line_total from QUANTITY, ITEM where QUANTITY.order_nbr = 123 and QUANTITY.item_nbr = ITEM.item_nbr; select sum(line_total) from TEMP;<br />
<br />
Note: The STATE-CITY-CUSTOMER hierarchy in Figure 14.2 is very deliberate. To be truly in the Third Normal Form, no redundant information is allowed. As such, a user’s seemingly simple query is complex to the system. For example, the SQL calculating the sum of all orders for the Western region looks very complex and involves the five-way table join, as follows: create table TEMP as select (QUANTITY.quantity_sold * ITEM.list_price) line_total From QUANTITY, ITEM, CUSTOMER, CITY, STATE file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch14/468-473.html (1 of 3)4/03/2005 6:16:35<br />
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where QUANTITY.item_nbr and ITEM.cust_nbr and CUSTOMER.city_name and CITY.state_name and STATE.region_name<br />
<br />
= ITEM.item_nbr<br />
<br />
/* join QUANTITY and ITEM */<br />
<br />
= CUSTOMER.cust_nbr<br />
<br />
/* join ITEM and CUSTOMER */<br />
<br />
= CITY.city_name<br />
<br />
/* join CUSTOMER and CITY */<br />
<br />
= STATE.state_name<br />
<br />
/* join CITY and STATE */<br />
<br />
= 'WEST';<br />
<br />
In reality, sufficient redundancy eliminates the CITY and STATE tables. The point is clear: A manager analyzing a series of complete order totals requires a huge amount of realtime computation. This process arrives at the basic tradeoff. For true freedom from redundant data, query time demands a price. In practice, the Third Normal Form database generally evolves into a STAR schema as you create a fact table to hold the quantity for each item sold (see Figure 14.9).<br />
<br />
Figure 14.9 The STAR query E/R model. At first glance, it’s hard to believe this is the same data as the normalized database. The new fact table contains one row for each item on each order, resulting in a tremendous amount of redundant key information in the table. It should be obvious that the STAR query schema requires far more disk space than a Third Normal Form database. Also, the STAR schema is most likely a read-only database because of the widespread redundancy introduced into the model. Finally, the widespread redundancy makes updating difficult (if not impossible) for the STAR schema. Notice the dimension tables around the fact table. Some of the dimension tables contain data that is added to queries with joins. Other dimensions, such as the Region dimension, contain no data. What purpose, then, does this STAR schema achieve with huge disk space consumption and a read-only restriction? Using the STAR schema in Figure 14.9, let’s formulate SQL queries for rapid retrieval of desired information. For example, identifying the total cost for an order is simple, as seen in the following code: select sum(total_cost) order_total from FACT where FACT.order_nbr = 123; It is clear that the new structure makes the realtime query faster and simpler. Consider the result if the goal is to analyze information by aggregate values using this schema. Suppose that the manager needs the breakdown of regional sales. The data by region is not available, but the FACT table supplies the answer. Obtaining the sum of all orders for the Western region is now simple, as seen in the following code: select sum(total_cost) from FACT where region = 'WEST' The merits of the STAR schema should now be apparent, but we need to note some other ways to represent time-oriented data suitable for OLAP type systems, namely, the multidimensional database architecture, as seen in Oracle Express.<br />
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It should now be clear to the reader how a proper design can be critical for good database performance. While far from being an exhaustive description of all of the relational design techniques, this chapter has focused on basic principles that will help to ensure that your WebServer database performs as quickly as possible. Once a good logical model has been created, it is critical to translate the logical model into an Oracle implementation capable of performing at optimal speed. Oracle involves many design issues, and in this chapter we’ve taken a look at how some physical design models can be used to exploit client/server performance. We have come to believe that response time is one of the most critical factors to the success of any database. Regardless of how well the system was analyzed or implemented—no matter how flashy the GUI interface—if the system fails to deliver data in a timely fashion, the project is doomed. Now that we have reviewed logical database design, let’s move on to the physical implementation of WebServer databases.<br />
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CHAPTER 15 Physical Oracle Design When creating a WebServer application, you must pay careful attention to the components that might affect system response time. These considerations include WebServer’s interaction with the Internet, Web Listener, Web Request Broker, and Oracle databases. Unfortunately, you have virtually no control over the Internet’s speed and very little control over the Web Listener and Web Request Broker. Oracle’s Web Listener and Web Request Broker have both been preoptimized by Oracle and cannot be tuned by adjusting any of their parameters. However, you can control how these components interact with your Oracle databases. More than other online applications, special consideration must be given to Oracle databases. Database transactions must be serviced efficiently to ensure that Web pages are sent to end users quickly. This chapter takes a look at the physical Oracle database design issues that can influence the performance of your WebServer applications. The topics in this chapter include the use of table replication with snapshots, referential integrity, index placement, and Oracle’s parallel facilities. The overall focus is on the use of physical database techniques for creating high-performance Oracle WebServer applications. Without an effective physical design, no amount of tuning will significantly improve performance. Hence, it is critical to any WebServer effort that you derive the optimal performance from all of your Oracle database servers.<br />
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Replication With Oracle Snapshots Oracle snapshots are used to create read-only copies of tables in other Oracle databases. Table replication is a highly effective way to avoid time-consuming and expensive cross-database joins of tables. As we know, an SQL join with a table at a remote server will be far slower than a join with a local table. The network overhead also increases as Oracle retrieves and transfers data across the network. The prudent use of replicated tables can greatly improve the response time for WebServer applications. It’s interesting to note that the general attitude about data replication has shifted dramatically in the past 10 years. In the 1980s, table replication was too expensive, both in terms of disk costs and the processing costs to update redundant tables. Also, academia believed that there was no substitute for the Third Normal Form database, and students were taught Codd’s Rules of Normalization as if the rules were physical laws of nature. Today, the practical realities of cheap disks and distributed processing have made replication an inexpensive and viable alternative to expensive crossdatabase joins. Table replication has proven to be stable and has been so successful within Oracle version 7 that Oracle version 7.3 is now introducing the concept of updatable snapshots. Snapshot is the term used by Oracle to implement their table replication strategy. However, table replication is not to be used indiscriminately, and the following several guidelines exist for using replicated tables in a WebServer application: • The replicated table should be read-only—Obviously, a table snapshot cannot be updated because the master copy of the table is on another server. • The replicated table should be relatively small—Ideally, a replicated table is small enough that the table can be dropped and re-created each night, or the refresh complete option can be used. Of course, large tables can be replicated with the refresh fast option, but this involves a complicated mechanism for holding table changes and propagating them to the replicated table. • The replicated table should be frequently accessed—It does not make sense to replicate a table if it is only referenced a few times per day, because the cost of the replication would outweigh the cost of the cross-database join. Despite any claims by Oracle to the contrary, only tables that meet the listed criteria should be placed in snapshots. In practice, snapshots are not maintenance-free, and many points of failure are possible—especially if the snapshot is created with the refresh fast option. Problems can occur writing to the SNAPSHOT_LOG table, and SQL*Net errors can cause failures of updates to transfer to the replicated tables.<br />
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How To Create Oracle Snapshots A snapshot is created on the destination system with the create snapshot SQL command, and the remote table is immediately defined and populated from the master table. After a snapshot has been created, it may be refreshed periodically. There are two types of refreshing in Oracle: complete and fast. A complete refresh can be done in several ways, but most savvy Oracle developers drop and re-create the snapshots with a Unix cron job to achieve full refreshes, especially if the table is small and easily recreated. Optionally, tables can be refreshed with only the changes made to the master table. This requires additional work on the slave database to create an Oracle refresh process (in the init.ora) and the definition of a snapshot log on the master database (see Figure 15.1).<br />
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Figure 15.1 A high-level overview of Oracle snapshots. Several steps need to be completed by the Oracle database administrator before your Oracle system is ready to use snapshots. First, the DBA needs to run catsnap.sql, which can be found in your $ORACLE_HOME/rdbms/admin directory. This script file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/475-478.html (1 of 4)4/03/2005 6:16:36<br />
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will populate the Oracle dictionary with the necessary system tables to manage the snapshots. The DBA also needs to run dbmssnap.sql, which can be found in the $ORACLE_HOME/rdbms/admin directory. This script creates the stored procedures that can be used to manipulate the snapshots. The following parameters must also be added to the init.ora file for each Oracle instance: • snapshot_refresh_interval=60—This sets the interval (in minutes) for the refresh process to wake up. • snapshot_refresh_processes=1—This is the number of refresh processes on the instance (the minimum is 1). • snapshot_refresh_keep_connections=FALSE—This specifies whether the database should keep remote connections after refreshing the tables. Always use FALSE. For snapshots that are small enough to be totally repopulated, it is recommended that the following steps are followed to re-create the snapshot from scratch. Note that it is possible to do a refresh complete or a refresh force rather than a cron job, but using a cron is a simple way to guarantee that the replicated table will be fully repopulated. To avoid the refresh fast option with a Unix cron, the following two steps are required: 1. Create the snapshot with the refresh complete option. 2. Alter oracle.cron to drop and re-create the snapshot. For snapshots on large tables, you may want to use the refresh fast option. To use refresh fast, the following steps are required: 1. Destination system—Create the snapshot with the refresh fast option signed on as user SYS. (Be sure to define a database link with connect to xxx identified by zzz and ensure that user xxx has select privileges against the master table.) 2. Master system—Create a snapshot log on each master table. 3. Bounce the destination system to begin the refreshes based on the interval specified in the create snapshot. Listing 15.1 shows an example of a snapshot that reads a table from an instance called fairport. Listing 15.1 Example of a snapshot with periodic refreshing. CONNECT sys/xxxx; DROP PUBLIC DATABASE LINK fairport; CREATE PUBLIC DATABASE LINK fairport CONNECT TO db_link IDENTIFIED BY db_pass USING 'fairport'; ———————————————————————————— DROP SNAPSHOT my_replicated_table; ———————————————————————————— CREATE SNAPSHOT my_replicated_table file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/475-478.html (2 of 4)4/03/2005 6:16:36<br />
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PCTFREE 10 PCTUSED 40 TABLESPACE ts2 STORAGE (initial 60k next 10k pctincrease 1) REFRESH FAST START WITH SYSDATE NEXT (sysdate+1) + 3/24 AS SELECT * FROM ORACLE.my_master_table@fairport; GRANT ALL ON my_replicated_table TO PUBLIC; —****************************************************** — Add the appropriate synonyms for the snapshots... —****************************************************** CONNECT /; CREATE PUBLIC SYNONYM snap$_my_replicated_table FOR ops$oracle.snap$_my_replicated_table; In Listing 15.1, you can see that the my_replicated_table table is refreshed each morning at 3:00 AM, and the read-only name snap$_my_replicated_table has been replaced with synonym my_replicated_table. Following is an example of the snapshot log syntax that needs to be run on the master database: CREATE SNAPSHOT LOG ON employee_table TABLESPACE ts2 STORAGE (initial 20k next 20k); The dbms_snapshot.refresh_all procedure can be run at any time on the destination system to refresh the snapshot tables. To force a refresh of an individual table, execute the following procedure: EXECUTE<br />
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dbms_snapshot.refresh('office','f');<br />
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Note: Any refresh errors are written to the alert.log file.<br />
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The snapshot log is a table that resides in the same database as the master table, which can be seen in the dba_tables view as a table with the name MLOG $_TABLENAME. In our example, the snapshot log would be called MLOG $_EMPLOYEE. Even with Oracle’s distributed features, it is still far faster to process a table on a local server than it is to process a remote table across SQL*Net’s distributed communication lines. As such, table replication is a very desirable technique for improving processing speeds. Several factors influence the decision about replicating tables. The foremost considerations are the size of the replicated table and the volatility of the tables. Large, highly active tables with many updates, deletes, and inserts will require a lot of system resources to replicate and keep synchronized with the master table. Smaller, less active tables would be ideal candidates for replication, because the creation and maintenance of the replicated table would not consume a high amount of system resources.<br />
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Oracle’s snapshot facility is relatively mature and generally works as noted in the Oracle documentation. However, the flexibility of the snapshot tool gives the developer many choices concerning how the snapshot will be created and refreshed. You can refresh a replicated table in full, recreate a snapshot at will, choose to periodically refresh a snapshot, and use database triggers to propagate changes from a master table to a snapshot table. Although the choice of techniques depends on the individual application, some general rules apply. If a replicated table is small and relatively static, it is usually easier to drop and re-create the snapshot than to use Oracle’s refresh complete option. A crontab file can be set up to invoke the dropping and re-creation of a snapshot at a predetermined time each day—completely refreshing the entire table. Another popular alternative to a snapshot is the use of Oracle’s distributed SQL to create a replicated table directly on the slave database. In the following example, the New York database creates a local table called EMP_NY, which contains New York employee information from the master employee table at corporate headquarters: create table emp_ny as select emp_nbr, emp_name, emp_phone, emp_hire_date from emp@hq where department = 'NY'; Very large replicated tables consume too much time in dropping and re-creating a snapshot or using the refresh complete option. For static tables, a snapshot log would not contain very many changes—we could direct Oracle to propagate the changes to the replicated table at frequent intervals. Let’s take a look at the different refresh intervals that can be specified for a snapshot. The following code tells Oracle to apply the snapshot log to the replicated table every seven days: create snapshot emp_snap1<br />
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refresh fast start with sysdate next sysdate+7 as select emp_nbr, emp_name from employee@hq where department = 'NY'; The next example code shows the command for a table to be refreshed each Tuesday at 6:00 AM: create snapshot EMP_SNAP1 refresh fast start with sysdate next next_day(trunc(sysdate),'tuesday')+6/24 as select emp_nbr, emp_name from employee@hq where department = 'NY'; For very static tables, you can specify refreshes to run quarterly. The following example refreshes a table completely on the first Tuesday of each quarter: create snapshot emp_snap1 refresh complete start with sysdate next next_day(add_months(trunc(sysdate,'q'),3),'tuesday') as select emp_nbr, emp_name from employee@hq where department = 'NY'; For dynamic tables that require refreshing daily, you can specify that the table is refreshed at a particular time each day. The following code refreshes a table every day, at 11:00 AM: create snapshot emp_snap1 refresh fast start with sysdate next sysdate+11/24 as select emp_nbr, emp_name from employee@hq where department = 'NY'; In addition to using the time range specified in the create snapshot syntax, you can also use Oracle stored procedures to get the same results. If you run the dbmssnap.sql script, you can refresh a snapshot by issuing the following command: execute dbms_snapshot.refresh('employee','c'); execute dbms_snapshot.refresh('employee','f'); execute dbms_snapshot.refresh('employee','?');<br />
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/* complete refresh */ /* forced refresh */ /* fast refresh */<br />
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Using Triggers To Update Snapshots What about replicated tables that require instantaneous propagation? Oracle version 7.3 offers updatable snapshots. Fortunately, users of previous releases of Oracle can also update snapshots by using database triggers to simulate the realtime propagation of changes from a master table to replicated tables. In the following example, an update trigger has been placed on the employee tables, and relevant changes will be propagated to the New York branch: Create trigger add_employee after insert on employee As If :dept = 'NY' then (insert into employee@NY values(:parm1, :parm2,:parm3); ); Your next question might be, What can we do about rows deleted from the employee table? Using the file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/478-482.html (2 of 3)4/03/2005 6:16:37<br />
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same technique, a delete trigger can be placed on the employee table to remove rows from the replicated tables: create trigger delete_employee after delete on employee as if :dept = 'NY' then (delete from employee@NY where emp_nbr = :employee_parm ); Using Snapshots To Propagate Subsets Of Master Tables As we have seen, snapshot replication is very handy for taking a master table and copying it to a remote location. But, what if we only want to replicate a portion of a table? Yes, Oracle provides a method for excluding certain rows and columns from the replicated table. For example, let’s assume that you are replicating a central employee table for use by your New York branch. However, you only want to replicate employee records for those who work in the New York branch, and you want to exclude confidential columns, such as the employees’ salaries. The snapshot would appear as follows: create snapshot emp_ny refresh fast start with sysdate next next_day(trunc(sysdate),'tuesday')+6/24 as select emp_nbr, emp_name, emp_phone, emp_hire_date from emp@hq where department = 'NY';<br />
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Using Referential Integrity With Oracle Referential Integrity (RI) rules ensure that one-to-many and many-to-many relationships are enforced within the relational schema. In addition, valid values can also be enforced with constraints. Constraints are especially important to WebServer applications, because WebServer allows constraint checking to take place at the database server, thereby relieving the Web client of the burden of checking constraints. Several types of constraints can be applied to Oracle tables to enforce referential integrity, including: • Check Constraint—This constraint validates incoming columns at row insert time. For example, rather than having an application verify that all occurrences of region are North, South, East, or West, a check constraint can be added to the table definition to ensure the validity of the region column. • Not Null Constraint—This constraint is used to specify that a column may never contain a NULL value. This is enforced at SQL insert and update time. • Primary Key Constraint—This constraint is used to identify the primary key for a table. This operation requires that the primary columns are unique, and Oracle will create a unique index on the target primary key. • References Constraint—This is the foreign-key constraint as implemented by Oracle. A references constraint is only applied at SQL insert and delete times. For example, assume a one-to-many relationship between the EMPLOYEE and DEPENDENT tables—each employee may have many dependents, yet<br />
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each dependent belongs to only one employee. The references constraint tells Oracle at insert time that the value in DEPENDENT.emp_num must match the EMPLOYEE.emp_num in the employee row, thereby ensuring that a valid employee exists before the dependent row is added. At SQL delete time, the references constraint can be used to ensure that an employee is not deleted if rows still exist in the DEPENDENT table. • Unique Constraint—This constraint is used to ensure that all column values within a table never contain a duplicate entry. Notice the distinction between unique and primary key. While both of these constraints create a unique index, a table may contain only one primary key constraint column—but it may have many unique constraints on other columns. Referential integrity usually needs to be double coded: once for the database and again within the application. For example, in a multipart SQL*Form, you may not become aware of an RI violation until you are many pages into the form and your form attempts to commit. In WebServer applications, you do not have the luxury of making a lot of queries against the database, and you need to be careful to keep the Oracle transactions as few as possible. Referential integrity maintains business rules. Relational systems allow control of business rules with constraints, and RI rules form the backbone of relational tables. For example, RI ensures that a row in the CUSTOMER table is not deleted if the ORDER table contains dependents for that employee (see Figure 15.2).<br />
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Figure 15.2 An example of referential integrity. It is clear that enforcing this business rule in our new distributed environment is a real challenge. While it is relatively simple to tell an Oracle system not to delete a row from its CUSTOMER table if rows for that employee exist in the ORDER table, it is not simple to enforce this rule when the CUSTOMER table resides in a Sybase database and the ORDER table resides within Oracle. The solution is to remove the database RI rules from each database, remembering to manually replicate the RI rules using procedural code within the application. This essentially creates your own customized RI within the application.<br />
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Indexes And Oracle Performance In Oracle, an index is used to speed up the time required to access table information. Internally, Oracle indexes are B-tree data structures, in which each tree node may contain many sets of key values and row IDs. In general, Oracle indexes exist for the purpose of preventing full-table scans. Fulltable scans have two problems, the most important being the time lost in servicing a request as each and every row of a table is read into Oracle’s buffer pool. The second problem associated with full-table scans is that they cause performance degradation at the system level. All other tasks on the system may have to incur additional I/O, because the buffer block held by competing tasks will have been flushed by the fulltable scan. As blocks are flushed from the buffer pool, other tasks incur additional I/Os to reread information that would have remained in the buffer pool if the full-table scan had not been invoked. In general, just about any Oracle table will benefit from the use of indexes. The only exception to this rule would be a very small table that can be read in less than two physical I/Os. Two physical I/Os are used as the guideline because Oracle needs to perform at least one I/O to access the root node of the index tree and another I/O to retrieve the requested data. For example, assume that a lookup table contains rows of 25 bytes each, and you have configured Oracle to use 4 K block sizes. Because each data block would hold about 150 rows, using an index for up to 300 rows would not make the processing any faster than a full-table scan. If you plan to use the Oracle parallel query facility, all tables specified in the SQL query must be optimized for a full-table scan. If an index exists, the cost-based optimizer must be used with a hint to invalidate the index in order to use parallel query. For the rule-based optimizer, indexes can be turned off by using an Oracle<br />
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function in the where clause. One important concept in indexing is the selectivity, or the uniqueness, of the values in a column. To be effective, an index column must have many unique values. Columns that have only a few values (e.g., sex = m/f, status = y/n) would not be good candidates for indexing. Similar to the index itself, the sparse distribution of values would be less efficient than a full-table scan. To see the selectivity for a column, compare the total number of rows in the table with the number of distinct values for the column. For example: select count(*) from EMPLOYEE; select distinct status from EMPLOYEE; Another concept used in indexing is called distribution, which refers to the frequency that each unique value is distributed within the database. For example, we may have a state_abbreviation column that contains 1 of 50 possible values. This would be acceptable to use as an index column, provided that the state abbreviations are uniformly distributed across the rows. However, if 90 percent of the values are for New York, then the index will not be very effective. Oracle has addressed the index data distribution issue with the analyze table command. When using Oracle’s costbased SQL optimizer, analyze table will look at both the selectivity and distribution of the column values. If they are found to be out-of-bounds, Oracle may decide not to use the index. Oracle recommends the following guidelines when considering whether to use an index on a column: • Columns frequently referenced in SQL where clauses are good candidates for an index. • Columns used to join tables (primary and foreign keys) should be indexed. • Do not use a B-tree index on columns with poor selectivity. Any column with less than 10 percent of unique values should be indexed as a bitmap index. • Frequently modified columns are not good candidates for indexing because excessive processing is necessary to maintain the structure of the index tree. • Do not index columns used in SQL where clauses using Oracle functions or operators. For example, an index for last_name will not be effective if it is referred to in the SQL as upper(last_name). • When using referential integrity, always create an index on the foreign key.<br />
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Tuning Queries With Indexes As a general rule, indexes will always increase the performance of a database query. In situations where a query intends to sweep a table in the same sequence that the rows are physically stored, the indexes in some tables may actually hinder performance. For Oracle, indexes are recommended for two reasons: to speed the retrieval of a small set of rows from a table and to presort result sets so that the SQL order by clause does not cause an internal sort. In order to use an index, the SQL optimizer must recognize that the column has a valid value for index use. This is called a sargeable predicate, and it’s used to determine the index access. Listing 15.2 shows some valid predicates, and Listing 15.3 shows invalid predicates. Listing 15.2 Viewing valid predicates. select * from EMPLOYEE where emp_no = 123; select * from EMPLOYEE where dept_no = 10; Listing 15.3 Viewing invalid predicates. select * from EMPLOYEE where emp_no = "123"; select * from EMPLOYEE where salary * 2 < 50000; select * from EMPLOYEE where dept_no != 10; Whenever a transformation to a field value takes place, the Oracle database will not be<br />
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able to use the index for that column. Some databases, such as DB2, will recognize a linear search and invoke a sequential prefetch to look ahead, reading the next data block while the previous data block is being fetched by the application. As a general rule, an SQL query that retrieves more than 15 percent of the table rows in a table will run faster if the optimizer chooses a full-table scan rather than an index. For example, assume that a student table has 1,000 rows, representing 900 undergraduate students and 100 graduate students. A nonunique index has been built on the student_level field that indicates underdgrad or grad. The same query will benefit from different access methods, depending upon the value of the literal in the where clause. The following query will retrieve 90 percent of the rows in the table and will run faster with a full-table scan rather than an index: select * from STUDENT where student_level = 'undergrad'; This next query will only access 10 percent of the table rows and will run faster by using the index on the student_level field: select * from STUDENT where student_level = 'grad'; Unfortunately, the Oracle database cannot predict in advance the number of rows that will be returned from a query. Many SQL optimizers will invoke an index access even though it may not always be the fastest access method. To remedy this problem, some dialects of SQL allow the user to control the index access. This is a gross violation of the declarative nature of theoretical SQL, in which the user does not control access paths. But, in practice, these extensions can improve performance. Oracle, for example, allows the concatenation of a null string to the field name in the where clause to suppress index access. The previous query could be rewritten in Oracle SQL to bypass the student_level index, as follows: select * from STUDENT where student_level||'' = 'undergrad'; The concatenation (||) of a null string to the field tells the Oracle SQL optimizer to bypass index processing for this field, instead of invoking a faster-running full-table scan. This a very important point. While SQL optimizers are becoming more intelligent about their databases, they still cannot understand the structure of the data and will not always choose the best access path. Concatenated Indexes A concatenated index is an index created on multiple columns. This type of index can greatly speed up queries where all of the index columns are specified in the queries’ SQL where clauses. For example, assume the following index on the STUDENT table: create index idx1 on STUDENT file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/486-489.html (2 of 4)4/03/2005 6:16:39<br />
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(student_level, major, last_name) ascending; The following concatenated index could be used to speed up queries that reference both student_level and major in the where clause: select student_last_name from STUDENT where student_level = 'undergrad' and major = 'computer science'; However, some queries using only major or student_level will not be able to use this concatenated index. In the following example, only the major field is referenced in the query, and a concatenated index cannot be used to service the query: select * from STUDENT where major = 'computer science'; In the following example, we see that student_level is the high-order index key, and the index will be used because student_level is the high-order index key: select last_name from STUDENT where student_level = 'plebe' order by last_name; Because student_level is the first item in the index, the leading portion of the index can be read, and the SQL optimizer will invoke an index scan. Why have we chosen to add the last_name to the index, even though it is not referenced in the where clause? Because Oracle will be able to service the request by reading only the index, and the rows of the STUDENT table will never be accessed. Also, because the order by clause asks to sort by last_name, Oracle will not need to perform a sort on this data. The not (!) operator will cause an index to be bypassed, and the query “show all undergrads who are not computer science majors” will cause a full-table scan: select * from STUDENT where student_level = 'undergrad' and major != 'computer science'; Here, the not condition isn’t a sargeable predicate and will cause a full-table scan.<br />
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Oracle Locking While most commercial database products provide mechanisms for locking and concurrency control, new issues emerge when using a relational database such as Oracle (see Figure 15.3). This problem is especially prevalent when a single Oracle task updates multiple remote servers, which is becoming increasingly common with distributed Oracle systems. The real nightmare begins when the remote servers are of differing architectures—for example, a distributed update to a relational and a network database. In these cases, the concurrency control is generally turned off for each database and is provided for inside the application program. After all, neither database can be expected to manage the internals of the other database.<br />
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Figure 15.3 An overview of Oracle locking. In addition to the technical issues, the popularity of client/server interfaces has also changed how concurrency is handled. Many client/server systems disable their Oracle database locking and rely upon procedural tricks to maintain data integrity at the server level. Oracle is one of these products, and we’ll discuss how to avoid contention by disabling Oracle locks.<br />
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Most programmers do not realize that database deadlocks occur frequently within database indexes. It’s important to note that a select of a single row from a database may cause more than one lock entry to be placed in the storage pool. When one row is locked, all affected index rows will also be locked. In other words, the individual row receives a lock, as well as each index node that contains the value for that row. If the “last” entry in a sorted index is retrieved, the database will lock all index nodes that reference the indexed value (in case the user changes that value). Many indexing schemes always carry the high-order key in multiple index nodes, so an entire branch of the index tree can be locked—all the way up to the root node of the index. While each database’s indexing scheme is different, some relational database vendors recommend that tables with ascending keys be loaded in descending order, so that the rows are loaded from Z to A on an alphabetic key field. Oracle recommends dropping indexes before large updates and re-creating the indexes after the rows have been loaded into the table. When an update or delete is issued against a row that participates in an index, the database will attempt an exclusive lock on the row, which requires the task to check for any shared locks held against the row as well as any index nodes that will be affected. Many indexing algorithms allow for the index tree to dynamically change shape, spawning new levels as items are added and condensing levels as items are deleted. For any table of consequential size, indexes are recommended to improve performance. Of course, an index requires additional disk space—a table with an index on each column will have indexes that consume more space than the table. Oracle will also update the indexes at runtime, as columns are deleted, added, or modified. This index updating can cause considerable performance degradation. For example, adding a row to the end of a table will cause Oracle to adjust the high-key value for each node in the table. One guideline for determining when to use an index involves examination of the SQL issued against a table. In general, the SQL can be collected, and each value supplied in each SQL where clause could be a candidate for inclusion in an index. Another common approach for determining where to create indexes is to run an explain plan for all SQL and carefully look for any full-table scans. The Oracle optimizers operate in such a fashion that Oracle will sometimes perform a full-table scan, even if an index has been defined for the table. This occurs most commonly when issuing complex n-way joins. If you are using rule-based optimization in Oracle, the structure of the SQL statement can be adjusted to force the use of an existing index. For Oracle’s cost-based optimizer, adding hints to the structure will ensure that all indexes are used. Keep in mind that indexes do much more than speed up an individual query. When full-table scans are performed on a large Oracle table, the buffer pool begins to page out blocks from other queries. This causes additional I/O for the entire database and results in poor performance for all queries—not just the offending full-table scan. Indexes are never a good idea for long descriptive columns. A column called employee_description would be a poor choice for an index because of its length and the inconsistency of the data within the column. If this column was 300 bytes, Oracle file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/489-492.html (2 of 4)4/03/2005 6:16:39<br />
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would be forced to do a huge amount of processing whenever the column is altered. Also, a field such as employee description would usually be referenced in SQL by using Oracle extensions, such as substr, like, and upper. Remember, these Oracle extensions invalidate the index. Suppose that an index has been created on employee_last_name. The following query would use the index: select status from EMPLOYEE where employee_last_name = 'burleson'; The following queries would bypass the index, causing a full-table scan: select status from EMPLOYEE where employee_last_name = lower('burleson'); select status from EMPLOYEE where employee_last_name like 'burl%'; Unlike other relational databases, Oracle cannot physically load a table in key order. Consequently, we can never guarantee that the rows in the table will be in any particular physical order. The use of an index can help whenever the SQL order by clause is used. For example, even if there are no complex where conditions, the presence of a where clause will assist the performance of the query. Consider the following SQL: select employee_last_name, employee_first_name from EMPLOYEE order by employee_last_name, employee_first_name; Building a multi-valued index on employee_last_name and employee_first_name will alleviate the need for an internal data sort. You can significantly improve the performance of the query by using the following SQL: create index emp_name on EMPLOYEE (employee_last_name, employee_first_name) ascending;<br />
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Oracle Constraints And Indexes In Oracle, some constraints will create an index on your behalf. For example, creating a primary key constraint on the EMPLOYEE table for the emp_id will create an index on the field, and it is not necessary to manually build an index (see Listing 15.4). Listing 15.4 Creating a primary key constraint. create table EMPLOYEE ( emp_nbr number constraint emp_ukey primary key (emp_nbr) using index pctfree 10 initrans 2 maxtrans 255 tablespace ts1 storage ( initial 256000 next 102400 minextents 1 maxextents 121 pctincrease 1 ), dept_name char(10) constraint dept_fk references DEPT on delete cascade, organization_name char(20) constraint org_fk references ORG on delete restrict, region_name<br />
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constraint state_check check (region_name in ('north', south', 'east', 'west')) ); Notice that you should always specify the location clause when declaring constraints. In the previous example, had the emp_ukey constraint been defined without the storage clause, the index would have been placed in whatever tablespace is specified by the table owner’s default tablespace, with whatever default storage parameters are in effect for that tablespace. Listing 15.4 shows some good examples of Oracle constraints. The first constraint is on the emp_nbr column—the primary key. When you use Oracle’s RI to specify a primary key, Oracle automatically builds a unique index on the column to ensure that no duplicate values are entered. The second constraint is on the dept_name column of the DEPT table. This constraint tells Oracle that it may not remove a department row if there are existing employee rows that reference that department. The on delete cascade tells Oracle that when the department row is deleted, all employee rows that reference that department will also be deleted. The next RI constraint on organization_name ensures that no organization is deleted if employees are participating in that organization. on delete restrict tells Oracle not to delete an organization row if any employee rows still reference the organization. Only after each and every employee has been set to another organization can the row be deleted from the organization table. The last RI constraint is called a check constraint. In a check constraint, Oracle verifies that a column is one of the valid values before inserting a row, but it will not create an index on the column. Using Multicolumn Indexes With Oracle When an SQL request is commonly issued using multiple columns, a concatenated or multicolumn index can be used to improve performance. Oracle supports the use of multivalued indexes, but there are some noteworthy limitations. Unlike other relational databases, Oracle requires that all columns in the index are sorted in the same order, either ascending or descending. For example, if we needed to index on employee_last_name ascending, followed immediately by gross_pay descending, we would not be able to use a multivalued index. Sometimes, two columns that have poor selectivity (i.e., columns having few unique values) can be combined into an index that has better selectivity. For example, we could combine a status field that has three values (good, neutral, and bad) with another column such as state_name (only 50 unique values), thereby creating a multivalued index that has far better selectivity than each column would have if indexed separately. Also, in Oracle version 7.3, bitmapped indexes can be defined for columns with poor selectivity, thereby improving SQL through put. Another reason for creating concatenated indexes is to speed the execution of queries that reference all of the values in an index. For example, consider the following query: select<br />
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employee_last_name, employee_status, employee_zip_code from EMPLOYEE order by employee_last_name; Now, you can create an index as follows: create index last_status_zip file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/493-495.html (2 of 3)4/03/2005 6:16:40<br />
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on EMPLOYEE (employee_last_name, employee_status, employee_zip_code) ascending; If this query were to be issued against the employee table, Oracle would never need to access any rows in the base table! All of the key values are contained in the index, and the high-order key (employee_last_name) is in the order by clause. Oracle can scan the index, retrieving the data without ever touching the base table. With the assistance of this feature, the savvy Oracle developer can add columns to the end of the concatenated index so that the base table is never touched. For example, if the previous query also returned the value of the employee_address column, this column could be added to the concatenated index, dramatically improving performance. In summary, the following guidelines apply when creating a concatenated index: • Use a composite index whenever two or more values are used in the SQL where the clause and the operators are joined by and. • Place the columns in the where clause in the same order as in the index, with data items added at the end of the index.<br />
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How Oracle Chooses Indexes It is interesting to note that the fastest execution for an individual task may not always be the best choice. For example, consider the following query against an employee table: select employee_name from EMPLOYEE where credit_rating = 'poor' and amount_due > 1000 and state = 'iowa' and job_description like lower('%computer%'); Here, you can see a query where a full-table scan would be the most efficient processing method. Because of the complex conditions and the use of Oracle extensions in the SQL, it might be faster to perform a full-table scan. However, the fast execution of this task may be done at the expense of other tasks on the system as the buffer pool becomes flushed. In general, the type of optimizer will determine how indexes are used. As we know, the Oracle optimizer can run as either rule-based or cost-based. As a general rule,<br />
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Oracle is intelligent enough to use an index if it exists, but there are exceptions to this rule. The most notable exception is the n-way join with a complex where clause. The rule-based optimizer will get confused and invoke a full-table scan on at least one of the tables, even if the appropriate foreign key indexes exist for all of the tables. The only remedy to this problem is to use the cost-based optimizer, which involves analyzing statistics for each table. You should also remember that Oracle will only use an index when the index column is specified in its “pure” form. The use of the substr, upper, lower, and other functions will invalidate an index. However, there are a few tricks to help you get around this obstacle. Consider the following two equivalent SQL queries: select * from EMPLOYEE where total_purchases/10 > 5000; select * from EMPLOYEE where total_purchases > 5000*10; The second query, by virtue of the fact that it does not alter the index column, would be able to use an index on the total_purchases column.<br />
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Parallelism And Client/Server The widespread acceptance of distributed processing and multitasking operating systems has heralded a new mode of designing and implementing business systems. Instead of the traditional linear design of systems, tomorrow’s system will incorporate massively parallel processing. The result? Many tasks may be concurrently assigned to service a database request. Indeed, the entire definition of data processing is changing. The corporate data resource has been expanded to include all sources of information, not just databases. Corporate information lies within email, scheduling programs, and many other nontraditional sources. Many companies are collecting this information without fully exploiting its value, and multiprocessing is an ideal technique for searching these huge amounts of free-form corporate information. Multitasking And Multithreading WebServer Processes Before tackling this subject, a distinction needs to be made between multitasking and multiprocessing. Multitasking refers to the ability of a software package to manage multiple concurrent processes, thereby allowing simultaneous processing. Although OS/2 and Windows NT are good examples of this technology, multitasking can be found within all midrange and mainframe databases. Multiprocessing refers to the use of multiple CPUs within a distributed environment where a master program directs parallel operations against numerous machines. Two levels of multiprocessing are possible. The first is the hardware level, where arrays of CPUs are offered. The second is the software level, where a single CPU can be partitioned into separate logical processors. The Prism software on the IBM mainframe environment is an example of multiprocessing technology.<br />
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In any case, programming for multiprocessors is quite different from linear programming techniques. Multiprocessing programming falls into two areas: data parallel programming and control parallel programming. Data parallel programming partitions the data into discrete pieces, running the same program in parallel against each piece. Control parallel programming identifies independent functions that are simultaneously solved by independent CPUs (see Figure 15.4).<br />
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Figure 15.4 An example of a parallel query. One of the greatest problems with implementing parallel processing systems is the identification of parallelism. Parallelism refers to the ability of a computer system to perform processing on many data sources in the same instant. Traditionally, database applications were linear in nature. Today’s systems have many opportunities for parallel processing. Parallelism is especially important for processes such as scientific applications that benefit from having hundreds—or even thousands—of processors working together to solve a problem. The same concept of parallelism applies to very large databases. If a query can be split into subqueries where each subquery is assigned to a processor, the response time for the query can reduce by a factor of thousands (see Figure 15.5).<br />
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Figure 15.5 The performance benefits of adding processors.<br />
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A review of the past 30 years makes it clear that tremendous improvements have been made in the speed of processors. At the same time, the prices of processors have continued to decline. However, this trend cannot continue forever. The physical nature of silicon processors has been pushed to its limit and is now reaching a diminishing point of return. In order to continue to enjoy increases in performance, either silicon needs to be replaced as a medium or new ways need to be devised to exploit parallelism in processing. Parallelism is an issue of scale. Where a linear process may solve a problem in 1 hour, a parallel system with 60 processors should be able to solve the problem in 1 minute, as demonstrated in Figure 15.5. In some instances, this statement would be analogous to the statement that one woman takes nine months to have a baby, so nine women should be able to produce a baby in one month. Speed can only be improved in situations where parallel processing is appropriate, which excludes traditional linear systems where one process may not begin until the preceding one ends. Other facets to parallel processing can be extremely valuable. A query against a very large database can be dramatically improved if the data is partitioned. For example, if a query against a text database takes one minute to scan a terabyte, then partitioning the data and processing into 60 pieces would result in a retrieval time of one second. Another key issue is the balancing of the CPU processing with the I/O processing. In a traditional data processing environment, the systems are not computationally intensive, and most of the elapsed time is spent waiting on I/O. However, this does not automatically exclude business systems from taking advantage of multiprocessing.<br />
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A continuum of processing architecture exists for parallel processing. On one end of the spectrum you find a few powerful CPUs loosely connected; on the other end is a large number of small, tightly coupled processors. Parallelism can be easily identified in a distributed database environment. For the database administrator, routine maintenance tasks such as export/import operations can be run in parallel, reducing the overall time required for system maintenance. In an open systems environment, parallelism may be simulated easily by using a remote mount facility. With a remote mount, a data file may be addressed directly from another processor, even though the data file physically resides on another machine. SMP Vs. MPP Processing SMP, or symmetrical multiprocessing, describes an architecture where many CPUs share a common memory area and I/O buffer. This type of architecture is not scaleable, as additional processors must compete for the shared memory and I/O resources. On the other hand, massively parallel processors (MPP) describes an architecture where many independent processors share nothing, operating via a common I/O bus. An MPP system can add processors without impeding performance, and performance will actually increase as processors are added.<br />
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Using Oracle’s Parallel Query With Oracle version 7.2, some powerful new features have been introduced to allow parallel processes to be used against the Oracle database. These features include: • Parallel create table as select • Parallel query • Parallel index building Please note that the new features of Oracle versions 7.2 and 7.3 will not be activated unless the following init.ora parameter has been used: COMPATIBILITY=7.3.0.0.0 Also, note that it is not necessary to have parallel processors (SMP or MPP) in order to use and benefit from parallel processing. Even on the same processor, multiple processes can be used to speed up queries. Oracle parallel query options can be used with any SQL select statements—the only restriction being that the query performs a full-table scan on the target table. Parallel queries are most useful in distributed databases where a single logical table has been partitioned into smaller tables at each remote node (see Figure 15.6). For example, an employee table ordered by employee name may be partitioned into an employee table at each remote database, such that you have a phoenix_employee, a los_angeles_employee, and so on. This approach is very common with distributed databases, where local autonomy of processing is important. However, what about the needs of those in corporate headquarters? How can they query all of these remote file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch15/498-502.html (2 of 4)4/03/2005 6:16:41<br />
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tables as a single unit and treat the logical employee table as a single entity?<br />
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Figure 15.6 An example of Oracle’s parallel query. While this splitting of a table according to a key value violates normalization theory, it can dramatically improve performance for individual queries. For large queries that span many logical tables, the isolated tables can be easily reassembled using Oracle’s parallel query facility, as follows: create view all_employee as select * from phoenix_employee@phoenix UNION ALL select * from los_angeles_employee@los_angeles UNION ALL select * from rochester_employee@rochester;<br />
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Note: The @ references refer to SQL*Net service names for the remote hosts.<br />
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We can now query the all_employee view as if it were a single database table, and Oracle parallel query will automatically recognize the union all parameter, firing off simultaneous queries against each of the three base tables. It’s important to note that the distributed database manager will direct each query to be processed at the remote location, while the query manager waits until each remote node has returned its result set. The following query will assemble the requested data from the three tables in parallel, with each query optimized separately: select employee_name from ALL_EMPLOYEE where total_purchases > 5000; The result set from each subquery is then merged by the query manager.<br />
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Summary Now that you understand the logical and physical database design issues that influence WebServer’s performance, let’s take a look at the performance and tuning issues that arise when creating a WebServer database. Let’s also look at how the tuning of SQL can help WebServer’s performance. We’ll do just that, in upcoming chapters.<br />
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CHAPTER 16 Database Performance And Tuning There are several factors that influence the performance of a WebServer application. While most of the factors are within the control of Oracle developers, some issues, such as Internet communications, are beyond the control of the Oracle developer. Consequently, we can only address performance and tuning of WebServer applications from the time a URL request is intercepted by the Web Listener until the completed request has been serviced and returned to the client. During this period, the following steps occur: 1. The request is intercepted by the Web Listener. 2. The request is forwarded to the CGI or the WRB. 3. The request is handed to Oracle. 4. Oracle services the request and passes the data back to the CGI or WRB. 5. The Web document is prepared and sent through the Web Listener to the requesting client. Oracle WebServer achieves acceptable performance through a variety of mechanisms. The following sections discuss some of the mechanisms affecting WebServer’s performance.<br />
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WebServer Performance Issues Response time with the Oracle WebServer is a function of the interaction between numerous components. The following components are listed in order of their impact on WebServer performance and speed:<br />
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1. 2. 3. 4. 5.<br />
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The Internet (data transmission across the Internet) The Oracle database (servicing data requests) The Web Listener (spawning Oracle requests) The Web Request Broker (building HTML pages) The PL/SQL agent (loading and executing Oracle stored procedures)<br />
<br />
We have no control over the speed of the Internet, but we do have some control over the Oracle components. Let’s take a look at some of the performance and tuning issues involved with the last two components. The Web Request Broker The Web Request Broker accepts connections from the Web Listener. These requests are in the form of URLs. When the WRB first receives a request, it interrogates the URL to determine the type of object being requested. The request could be for an Oracle stored procedure, a Java routine, or any routine that has been defined with a socket. The determination of the type of object being requested is a function of the pathname in the URL. The internal meaning of pathnames is governed by the WebServer configuration. For example, the WebServer may be configured so that URL requests beginning with /oraproc are passed to the PL/SQL agent and URL requests beginning with /java are passed to the Java interpreter. The PL/SQL Agent Interacting with a PL/SQL agent is generally much easier than interacting with Oracle using LiveHTML or Java. In addition, the PL/SQL agent is much faster than it was in WebServer version 1.0. This is due to a change in the architecture, whereby each instance of the PL/SQL agent stays connected to Oracle between database requests. Continuous connection does not mean that a run-unit connection is maintained with Oracle. Rather, it means that a communication connection to Oracle has been established, but no database connection has been made via SQL*Net. As you know, when someone establishes a connection to SQL*Plus, you can see the connection by selecting the V$SESSION view within Oracle. This is not the case with WebServer, because the PL/SQL agent only connects to Oracle during the servicing of the request. The servicing of a PL/SQL request consists of the following steps: 1. Retrieving the stored procedure from Oracle. 2. Executing the stored procedure. 3. Performing the specified database access. Because each HTTP request initiates a new SQL*Net session, Oracle is technically logging off and reestablishing an SQL*Net session each time a URL request is made. However, this process happens quickly because the Oracle server connection is maintained between URL requests.<br />
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Oracle Stored Procedures As objects such as stored procedures and triggers become more popular, more application code will move away from external programs and into the database engine. Oracle has been encouraging this approach in anticipation of the object-oriented features of Oracle8. We have even more reasons for using stored procedures with WebServer applications because stored procedures are the method used for all PL/SQL interfaces with Oracle. However, Oracle DBAs must be aware of the increased memory demands associated with stored procedures. DBAs must plan carefully for the increased memory requirements when processing logic within databases. Today, most Oracle databases have only a small amount of code in stored procedures—but this is rapidly changing. WebServer requirements aside, many compelling benefits can be derived by placing all Oracle SQL inside stored procedures. These benefits include: • Better performance—Stored procedures are loaded once into the SGA and remain there unless they become paged out. Subsequent executions of the stored procedure are far faster than external code. • Coupling of data with behavior—Relational tables can be coupled with the behaviors associated with them by using naming conventions. For example, if all behaviors associated with the EMPLOYEE table are prefixed with the table name (i.e., EMPLOYEE.hire, EMPLOYEE.give_raise), then the data dictionary can be queried to list all behaviors associated with a table (for instance, select * from dba_objects where owner = ‘EMPLOYEE’), and<br />
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code can be readily identified and reused. • Isolation of code—Because all SQL is moved out of the external programs and into stored procedures, the application programs are nothing more than calls to stored procedures. As such, it becomes very simple to swap out one database and swap in another. One of the foremost reasons why stored procedures and triggers function faster than traditional code is related to Oracle System Global Area (SGA). After a procedure has been loaded into the SGA, it will remain in the library cache until it’s paged out of memory. Items are paged out of memory based on a least-recently-used algorithm. Once loaded into the RAM memory of the shared pool, the procedure will execute very quickly. The trick is to prevent pool-thrashing during the period when many procedures are competing for a limited amount of library cache within the shared pool memory. Thrashing is the condition where stored procedures are flushed out of the library cache to make room for other stored procedures. When tuning Oracle, two init.ora parameters emerge as more important than all of the other parameters combined. These are the db_block_buffers and the shared_pool_size parameters. These two parameters define the size of the in-memory region that Oracle consumes on startup and determines the amount of storage available to cache data blocks, SQL, and stored procedures. Oracle also provides a construct called a package. Essentially, a package is a collection of functions and stored procedures that can be organized in a variety of ways. For example, functions and stored procedures for employees can be logically grouped together in an employee package, as follows: create package employee as function compute_raise_amount (percentage number); procedure hire_employee(); procedure fire_employee(); procedure list_employee_details(); end employee; Here we have encapsulated all employee “behaviors” into a single package that will be added into Oracle’s data dictionary. If we force our programmers to use stored procedures, the SQL moves out of the external programs and into the database, reducing the application programs into nothing more than a series of calls to Oracle stored procedures. As systems evolve and the majority of process code resides in stored procedures, Oracle’s shared pool becomes very important. The shared pool consists of the following subpools: • • • •<br />
<br />
Dictionary cache Library cache Shared SQL areas Private SQL area (these exist during cursor open/cursor close)<br />
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• persistent area • runtime area As mentioned, the shared pool utilizes a least-recently-used algorithm to determine which objects are paged out of the shared pool. As this paging occurs, fragments, or discontiguous chunks of memory, are created within the shared pool. This means that a large procedure that initially fits into memory may not fit into contiguous memory when it’s reloaded after paging out. Consider the body of a package that has been paged out of an instance’s SGA because of other, more recent or frequent activity. Fragmentation will occur, and the server will not be able to find enough contiguous memory to reload the package body, resulting in an ORA-4031 error.<br />
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Pinning WebServer Packages In The SGA To prevent paging, packages can be marked as nonswappable, which tells the database that after their initial load they must always remain in memory. This is called pinning or memory fencing. Oracle provides a procedure called dbms_shared_pool.keep to pin a package. Packages can be unpinned with dbms_shared_pool.unkeep.<br />
<br />
Note: Only packages can be pinned. Stored procedures cannot be pinned unless they are placed into a package.<br />
<br />
The choice of whether to pin a package in memory is a function of the size of the object and the frequency of its use. Very large packages that are called frequently might benefit from pinning, but any difference may go unnoticed because the frequent calls to the procedure have kept it loaded into memory. Therefore, because the object never pages out, the pinning has no effect. Also, the way procedures are grouped into packages may have some influence. Some Oracle DBAs identify high-impact procedures and group them into a single package, which is pinned in the library cache. In an ideal world, the shared_pool parameter of the init.ora should be large enough to accept every package, stored procedure, and trigger that may be used by an application. However, reality dictates that the shared pool cannot grow indefinitely, and wise choices must be made in terms of which packages are pinned and which are excluded from the pinning routine. Because of their frequent usage, Oracle recommends that the standard, dbms_standard, dbms_utility, dbms_describe, and dbms_output packages always be pinned in the shared pool. To illustrate how pinning works, the following snippet demonstrates how a stored procedure called sys.standard can be pinned: connect internal; @/usr/oracle/rdbms/admin/dbmspool.sql execute dbms_shared_pool.keep('sys.standard'); A stored procedure can be written to pin all of the recommended Oracle packages into the shared pool. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch16/507-511.html (1 of 3)4/03/2005 6:16:43<br />
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Following is what this type of script might look like: EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE EXECUTE<br />
<br />
dbms_shared_pool.keep('DBMS_ALERT'); dbms_shared_pool.keep('DBMS_DDL'); dbms_shared_pool.keep('DBMS_DESCRIBE'); dbms_shared_pool.keep('DBMS_LOCK'); dbms_shared_pool.keep('DBMS_OUTPUT'); dbms_shared_pool.keep('DBMS_PIPE'); dbms_shared_pool.keep('DBMS_SESSION'); dbms_shared_pool.keep('DBMS_SHARED_POOL'); dbms_shared_pool.keep('DBMS_STANDARD'); dbms_shared_pool.keep('DBMS_UTILITY'); dbms_shared_pool.keep('STANDARD');<br />
<br />
Automatic Repinning Of Packages While this pinning routine ensures that a package stays pinned while the Oracle instance is running, you may also want to ensure that a package gets pinned each time the Oracle instance is started. Users of Oracle for Unix may want to add code to the /etc/rc file to ensure that the packages are repinned after each database startup. The rc file is generally maintained by the Unix system administrator, and this process guarantees that all packages are repinned with each bounce of the box. A pinning script might look like this: [root]: more pin ORACLE_SID=mydata export ORACLE_SID su oracle -c "/usr/oracle/bin/svrmgrl /<<! connect internal; select * from db; @/usr/local/dba/sql/pin.sql exit; !" The Oracle DBA must also remember to run pin.sql whenever restarting the Oracle database. This is done by reissuing the pin command from inside svrmgrl immediately after the database has been restarted.<br />
<br />
How To Measure Pinned Packages How do we identify frequently accessed packages? The Oracle alert logs do not provide this information, and other methods must be found for sampling package usage. Listing 16.1 shows a handy script illustrating pinned packages in the SGA. This procedure could be run periodically and piped into a shell script that would maintain counts of the number of times each package has been called. Listing 16.1 Looking at pinned packages in the SGA. rem memory.sql Display used SGA memory for triggers, packages, and procedures SET PAGESIZE 60; COLUMN EXECUTIONS FORMAT 999,999,999; COLUMN Mem_used FORMAT 999,999,999; SELECT SUBSTR(owner,1,10) Owner, SUBSTR(type,1,12) Type, SUBSTR(name,1,20) Name, executions, sharable_mem Mem_used, SUBSTR(kept||' ',1,4) "Kept?" FROM v$db_object_cache WHERE TYPE IN ('TRIGGER','PROCEDURE','PACKAGE BODY','PACKAGE') file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch16/507-511.html (2 of 3)4/03/2005 6:16:43<br />
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ORDER BY EXECUTIONS DESC; Listing 16.2 shows the output of memory.sql. Listing 16.2 The output of memory.sql. SQL> @memory OWNER<br />
<br />
TYPE<br />
<br />
SYS SYS SYS SYS SYS SYS SYS SYS HRIS SYS SYS HRIS HRIS HRIS HRIS HRIS SYS SYS KIS HRIS HRIS SYS HRIS SYS SYS SYS GIANT HRIS<br />
<br />
PACKAGE PACKAGE BODY PACKAGE PACKAGE BODY PACKAGE PACKAGE BODY PACKAGE PACKAGE BODY PACKAGE PACKAGE PACKAGE BODY PACKAGE PACKAGE BODY PACKAGE BODY PACKAGE PACKAGE BODY PACKAGE PACKAGE BODY PROCEDURE PACKAGE PACKAGE BODY PACKAGE PROCEDURE PACKAGE BODY PACKAGE PACKAGE BODY PROCEDURE PROCEDURE<br />
<br />
NAME STANDARD STANDARD DBMS_ALERT DBMS_ALERT DBMS_LOCK DBMS_LOCK DBMS_PIPE DBMS_PIPE S125_PACKAGE DBMS_UTILITY DBMS_UTILITY HRS_COMMON_PACKAGE S125_PACKAGE HRS_COMMON_PACKAGE GTS_SNAPSHOT_UTILITY GTS_SNAPSHOT_UTILITY DBMS_STANDARD DBMS_STANDARD RKA_INSERT HRS_PACKAGE HRS_PACKAGE DBMS_DESCRIBE CHECK_APP_ALERT DBMS_DESCRIBE DBMS_SESSION DBMS_SESSION CREATE_SESSION_RECOR INIT_APP_ALERT<br />
<br />
EXECUTIONS 867,600 867,275 502,126 433,607 432,137 432,137 397,466 397,466 285,700 284,694 284,694 258,657 248,857 242,155 168,978 89,623 18,953 18,872 7,067 5,175 5,157 718 683 350 234 165 62 6<br />
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MEM_USED 151,963 30,739 3,637 20,389 3,140 10,780 3,412 5,292 3,776 3,311 6,159 3,382 30,928 8,638 11,056 3,232 14,696 3,432 4,949 3,831 36,455 12,800 3,763 9,880 3,351 4,543 7,147 10,802<br />
<br />
KEP YES YES NO NO YES YES NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO NO<br />
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You can determine the number of times a nonpinned stored procedure has been swapped out of memory and required to reload. To effectively measure memory, two methods are recommended. The first recommended method is to regularly run the estat-bstat utility (usually located in ~/rdbms/admin/utlbstat.sql and utlestat.sql) to measure SGA consumption over a period of time. Another handy method would be writing a snapdump utility to interrogate the SGA and note any exceptional information relating to the library cache. This would include the following measurements: • Data dictionary hit ratio • Library cache miss ratio • Individual hit ratios for all namespaces Also, be aware that the relevant parameter, shared_pool_size, is used for other objects besides stored procedures. This means that one parameter fits all, and Oracle offers no method for isolating the amount of storage allocated to any subset of the shared pool. Here is a sample report for gathering information relating to shared_pool_size. Let’s say you see that your data dictionary hit ratio is above 95 percent and your library cache miss ratio is very low. You also notice that there are over 125,000 reloads in the SQL area namespace. At this point, you may want to increase the shared_pool_size. When running this type of report, always remember that statistics are gathered from startup and the numbers may be skewed. For example, on a system that has been running for six months, the data dictionary hit ratio will be a running average over six months. Consequently, data from the V$ structures is meaningless if you want to measure today’s statistics. Some Oracle DBAs will run utlbstat.sql, wait a short period, and then run utlestat.sql. This sequence produces a report called report.txt, where values can be extracted. One alternative is shown in Listing 16.3, which shows short customized statistics from the V$ tables in Oracle. Listing 16.3 A sample Oracle statistics utility. ========================= DATA DICT HIT RATIO ========================= (should be higher than 90 else increase shared_pool_size in init.ora) Data Dict. Gets 41,750,549<br />
<br />
Data Dict. cache misses 407,609<br />
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DATA DICT CACHE HIT RATIO 99<br />
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Oracle Databases on the Web:Database Performance And Tuning<br />
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========================= LIBRARY CACHE MISS RATIO ========================= (If > 1 then increase the shared_pool_size in init.ora) executions 22,909,643<br />
<br />
Cache misses while executing 171,127<br />
<br />
LIBRARY CACHE MISS RATIO .0075<br />
<br />
========================= LIBRARY CACHE SECTION ========================= hit ratio should be > 70, and pin ratio > 70 ... NAMESPACE SQL AREA TABLE/PROCEDURE BODY TRIGGER INDEX CLUSTER OBJECT PIPE<br />
<br />
Hit ratio 84 98 98 98 0 31 100 99<br />
<br />
pin hit ratio 94 99 84 97 0 33 100 99<br />
<br />
reloads 125,885 43,559 486 1,145<br />
<br />
52<br />
<br />
Let’s take a look at the SQL*Plus script (shown in Listing 16.4) that generated Listing 16.3. Listing 16.4 The script that generated Listing 16.3. PROMPT PROMPT PROMPT PROMPT PROMPT PROMPT (should PROMPT<br />
<br />
========================= DATA DICT HIT RATIO ========================= be higher than 90 else increase shared_pool_size in<br />
<br />
init.ora)<br />
<br />
COLUMN "Data Dict. Gets" FORMAT 999,999,999 COLUMN "Data Dict. cache misses" FORMAT 999,999,999 SELECT sum(gets) "Data Dict. Gets", sum(getmisses) "Data Dict. cache misses", trunc((1-(sum(getmisses)/sum(gets)))*100) "DATA DICT CACHE HIT FROM v$rowcache; PROMPT PROMPT ========================= PROMPT LIBRARY CACHE MISS RATIO PROMPT ========================= PROMPT (If > 1 then increase the shared_pool_size in init.ora) PROMPT COLUMN "LIBRARY CACHE MISS RATIO" FORMAT 99.9999 COLUMN "executions" FORMAT 999,999,999 COLUMN "Cache misses while executing" format 999,999,999 SELECT sum(pins) "executions", sum(reloads) "Cache misses while (((sum(reloads)/sum(pins)))) "LIBRARY CACHE MISS RATIO" FROM v$librarycache; PROMPT PROMPT ========================= PROMPT LIBRARY CACHE SECTION PROMPT ========================= PROMPT hit ratio should be > 70, and pin ratio > 70 ... PROMPT<br />
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RATIO"<br />
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executing",<br />
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Oracle Databases on the Web:Database Performance And Tuning<br />
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COLUMN "reloads" FORMAT 999,999,999 SELECT namespace, trunc(gethitratio * 100) "Hit ratio", trunc(pinhitratio * 100) "pin hit ratio", reloads "reloads" FROM v$librarycache; Just as the wisdom of the 1980s dictated that data should be centralized, the 1990s have begun an era where SQL is also centralized and managed. With the centralization of SQL, many previously impossible tasks have become trivial. For example: • SQL can easily be identified and reused. • SQL can be extracted by DBAs, enabling explain plan utilities to be run to determine the proper placement of table indexes. • SQL can be searched, allowing for fast identification of “where used” information. For example, when a column changes definition, all SQL referencing that column can be quickly identified. As memory becomes less expensive, it will eventually become desirable to have all of the application’s SQL and code loaded into the Oracle library cache, where the code will be available quickly for execution by any external applications, regardless of platform or host language. The most compelling reasons for putting all SQL within packages are portability and code management. If all applications become “SQL-less,” with calls to stored procedures, then entire applications can be ported to other platforms without altering a single line of the application code. As the cost of memory drops, 500 MB Oracle regions will not be uncommon. Until that time, however, DBAs must carefully consider the ramifications of pinning a package in the SGA.<br />
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Oracle Triggers Many database systems now support the use of triggers that can be fired at specific events. The insertion, modification, or deletion of a record may fire a trigger; or a business event, such as place_order, may initiate a trigger. Oracle Corporation claims that the design of their triggers closely follows the ANSI/ISO SQL3 draft standard (ANSI X3H6), but Oracle triggers are more robust in functionality than the ANSI standard. Triggers are defined at the schema level of the system, and will fire whenever an SQL select, update, delete, or insert command is issued. Remember that a trigger is always associated with a single DML event. Deciding When To Use A Trigger The choice of when to use a trigger and when to use a stored procedure can have a profound impact on the performance of the system. In general, triggers are used when additional processing is required as a row is inserted into a table. For example, assume that whenever a customer row is added, the system is required to look for the customer in the BAD_CREDIT table. If the customer appears in the BAD_CREDIT table, then its shipping_status column is set to COD. In this case, a trigger on insert of customer can fire the PL/SQL procedure to do the necessary lookup and set the shipping_status field to its appropriate value. Oracle triggers have the ability to call procedures, and a trigger may include SQL statements, thus providing the ability to nest SQL statements. Oracle triggers are stored as procedures that may be parameterized and used to simulate object-oriented behavior. For example, assume that we want to perform a behavior called check_total_inventory whenever an item is added to an order. (See Figure 16.1.)<br />
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Figure 16.1 The relationship among objects, triggers, and SQL. The trigger definition would be: create trigger check_total_inventory after select of item for each row select count(*) into :count from quantity where item_num = :myitem if :count < item.total then ...... end if; Triggers can also be combined to handle multiple events, such as the reordering of an item when the quantity-on-hand falls below a predefined level, as follows: create trigger reorder before update on item for each row when (new.reorderable = 'y') begin if new.qty_on_hand + old.qty_on_order < new.minimum_qty then insert into reorder values (item_nbr, reorder_qty); new.qty_on_order := old.qty_on_order + reorder_qty; end if; end;<br />
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Oracle Hashing Oracle7 now supports the concept of hash clusters. A hash cluster is a construct that works with Oracle clusters and uses the hashkeys command to allow fast access to the primary key for the cluster, thereby reducing I/O for your WebServer application. To reduce I/O, Oracle relies on a hashing algorithm, which takes a symbolic key and converts it into a row ID (rowid). The hashing function ensures that the cluster key is retrieved in a single I/O, which is faster than reading multiple blocks from an index tree. Because a hashing algorithm always produces the same key each time it reads an input value, duplicate keys have to be avoided. In Oracle, these collisions result when the values of hashkeys are less than the maximum number of cluster key values. For example, if a hash cluster uses the cust_nbr field as the key, and we know that there will be 50,000 unique cust_nbr values, then we must be sure that the value of hashkeys is set to at least 50,000. Also, you should always round up your value for hashkeys to the next highest prime number. Following is an example of a hash cluster: create cluster my_cluster (customer_nbr varchar(10)) tablespace user1 storage (initial 50k next 50k pctincrease 1) size 2k hash is customer_nbr hashkeys 50000; Now a table is defined within the cluster: create table customer ( customer_nbr number primary key) cluster my_cluster (customer_nbr);<br />
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The size parameter is usually set to the average row size for the table. Oracle recommends using a hash cluster when the following are true: • Use hash clusters to store tables commonly accessed by where clauses that specify equalities. • Only use hash clusters when you can afford to keep plenty of free space on each database block for updates. This value is set by the pctfree statement in the create table parameter. • Only use hash clusters if you are absolutely sure that you will not need to create a new, larger cluster at a later time. • Do not use a hash cluster if your table is commonly accessed by full-table scans, especially if a great deal of extra space from future growth has been allocated to the hash cluster. In a full-table scan, Oracle will read all blocks of the hash cluster, regardless of whether they contain any data rows. • Do not use a hash cluster if any of the hash cluster keys are frequently modified. Changing the value of a hash key causes the hashing algorithm to generate a new location, and the database will migrate the cluster to a new database block if the key value is changed. This is a very time-consuming operation. Keep in mind that the total size of the index columns must fit inside a single Oracle block. If the index contains too many long values, additional I/O will be required and updates and inserts will cause serious performance problems. Note the sample hashing routine shown in Figure 16.2.<br />
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Figure 16.2 A sample hashing routine. The database designer may choose to make the buffer blocks large to minimize I/O if the application clusters record on a database page. If a customer record is only 100 bytes, we will not gain by retrieving 32,000 bytes in order to get the 100 bytes that we need. However, if we cluster the orders physically near the customer (on the same database page), and if I/O usually proceeds from customer to order, then we will not need further I/O to retrieve orders for the customer.<br />
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Oracle Clusters Clustering is a very important concept for improving Oracle performance. As you know, when accessing Oracle, reducing I/O always improves throughput and overall performance. The concept of a cluster is very similar to the use of the VIA set in the CODASYL Network database model, where member records are stored physically near parent records. For Oracle, clusters can be used to define common one-to-many access paths, and the member rows can be stored on the same database block as their owner row. For example, assume that we have a one-to-many relationship between customers and orders. If our application commonly accesses the data from customer to order, we can cluster the order rows on the same database block as the customer row. In this way, we’ll receive the list of all orders for a customer in a single I/O. (See Figure 16.3.) Of course, we will need to size the database blocks with db_block_size so that an entire order will fit onto a single database block.<br />
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Figure 16.3 A sample Oracle cluster. We need to note one important issue: While a cluster will tremendously improve performance in one direction, queries in the other direction will suffer. For example, consider the many-to-many relationship between customers and orders. We have the junction table, ORDER_LINE, at the intersection of this many-to-many relationship and we need to decide which owner, ORDER or ITEM, will be the anchor for our cluster. If we commonly traverse from ORDER to ITEM (e.g., displaying an order form), it would make sense to cluster the ORDER_LINE records on the same database block as their ORDER owner. If, on the other hand, we commonly traversed from ITEM to ORDER (e.g., requesting the details for all orders containing widgets), file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch16/518-521.html (1 of 3)4/03/2005 6:16:46<br />
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we would cluster the ORDER_LINE rows near their ITEM owner. If we cluster on the ORDER owner, database queries that display order forms will be very fast, while queries in the other direction will have to do additional I/O.<br />
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Oracle Parallel Query One of the most exciting performance features of Oracle version 7.3 and above is the ability to partition an SQL query into subqueries and dedicate separate processors to concurrently service each subquery. At this time, parallel query is useful only for queries that perform full-table scans on long tables, but the performance improvements can be dramatic. Here’s how it works. Instead of having a single query server manage the I/O against a table, parallel query allows the Oracle query server to dedicate many processors to acess the data, simultaneously, as shown in Figure 16.4.<br />
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Figure 16.4 A sample parallel query. To be most effective, the table should be partitioned onto separate disk devices, such that each process can do I/O against its segment of the table without interfering with the other simultaneous query processes. However, the client/server environment of the 1990s relies on RAID or a logical volume manager (LVM), which scrambles data files across disk packs in order to balance the I/O load. Consequently, full utilization of parallel query involves striping a table across numerous data files, each on a separate device. Even if your system uses RAID or LVM, some performance gains are still available with parallel query. In addition to using multiple processes to retrieve the table, the query manager will also dedicate numerous processes to simultaneously sort the result set. (See Figure 16.5.)<br />
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Figure 16.5 A sample parallel sort. Parallel query works best with symmetric multiprocessor (SMP) boxes, which have more than one internal CPU. Also, it is important to configure the system to maximize the I/O bandwidth, either through disk striping or high-speed channels. Because of the parallel sorting feature, it is also a good idea to beef up the memory of the processor. While sorting is no substitute for using a presorted index, the parallel query manager will service requests far faster than a single process. The data retrieval will not be significantly faster, though, because all of the retrieval processes will be competing for a channel on the same disk. Each sort process has its own sort area (as determined by the sort_area_size init.ora parameter), which speeds along the sorting of the result set.<br />
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In addition to full-table scans and sorting, the parallel query option also allows parallel processing for merged joins and nested loops.<br />
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Invoking the parallel query option requires all indexing to be bypassed. And, most importantly, the execution plan for the query specifies a full-table scan. If the output of the explain plan does not indicate a full-table scan, the query can be forced to ignore the index by using query hints. The number of processors dedicated to service an SQL request is ultimately determined by the Oracle query manager, but the programmer can specify the upper limit on the number of simultaneous processes. When using the cost-based optimizer, the parallel hint can be embedded into the SQL to specify the number of processes. For example: select /*+ full(EMPLOYEE_TABLE) parallel(EMPLOYEE_TABLE, employee_name from EMPLOYEE_TABLE where emp_type = 'SALARIED';<br />
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4) */<br />
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If you are using SMP with many CPUs, you can issue a parallel request and leave it up to each Oracle instance to use their default degree of parallelism, as follows: select /*+ full(EMPLOYEE_TABLE) parallel(EMPLOYEE_TABLE, default, default) */ employee_name from EMPLOYEE_TABLE where emp_type = 'SALARIED'; Several important init.ora parameters have a direct impact on parallel query: • sort_area_size—The higher the value, the more memory available for individual sorts on each parallel process. Note that the sort_area_size parameter allocates memory for every query on the system that invokes a sort. For example, if a single query needs more memory and you increase the sort_area_size, all Oracle tasks will allocate the new amount of sort area, regardless of whether they will use all of the space. • parallel_min_servers—The minimum number of query servers active on the instance. System resources are involved in starting a query server, so having the query server started and waiting for requests will speed up processing. Note that if the actual number of required servers is less than the value of parallel_min_servers, the idle query servers will be consuming unnecessary overhead, and the value should be decreased. • parallel_max_servers—The maximum number of query servers allowed on the instance. This parameter file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch16/521-524.html (1 of 2)4/03/2005 6:16:46<br />
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will prevent Oracle from starting so many query servers that the instance is unable to service all of them properly. To see how many parallel query servers are busy at any given time, the following query can be issued against the v $pq_sysstat table: select * from v$pq_sysstat where statistic = 'Servers Busy'; STATISTIC Servers Busy<br />
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VALUE 30<br />
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In this case, we see that 30 parallel servers are busy. Do not be misled by this number. Parallel query servers are constantly accepting work or returning to idle status, so it is a good idea to issue the query many times over a one hour period. Only then will you have a realistic measure of how many parallel query servers are being used.<br />
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Summary Now that we have covered the some of the tricks that can be used within Oracle to speed up WebServer queries, let’s take a look at the broader Oracle picture and explore how Oracle tuning can help WebServer at the system level. In the next chapter, we’ll explore how Oracle memory (SGA) can be tuned so that you’ll achieve maximum performance from your WebServer data requests.<br />
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CHAPTER 17 Tuning Oracle SQL Up until now, you’ve been reading about the physical Oracle database issues involved when creating a WebServer application; now let’s take a look at how Oracle’s SQL can be tuned to ensure optimal performance from WebServer. While several books have been devoted to the efficient use of Oracle SQL, only a handful of general rules and guidelines are effective in guaranteeing optimal performance from Oracle databases. This chapter focuses on the basic techniques for quickly achieving the maximum SQL performance with the least amount of effort. Topics in this chapter include: • • • • • •<br />
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Reviewing tips for creating efficient SQL Using index predicates Using concatenated indexes Improving performance using temporary tables Tuning with the rule-based optimizer Using hints with the cost-based optimizer<br />
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Tuning Oracle SQL Syntax SQL is a declarative language, so you can write a query many ways. And while each query might return identical results, the execution time can vary dramatically. To illustrate this concept, let’s consider a small employee table with 100 rows and an file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/525-528.html (1 of 3)4/03/2005 6:16:47<br />
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index on sex and hiredate. Let’s say you issue the following query to retrieve all female employees who have been hired within the last 90 days. The query uses Oracle’s rule-based optimizer, as follows: select emp_name from EMPLOYEE where sex = 'F' and hiredate between sysdate-90 and sysdate; Because the table has only 100 rows, the most efficient way to service this request would be to use a full-table scan. However, Oracle will walk the index that exists, performing dozens of extra I/Os as it reads the index tree to access the rows in the table. This simplistic example serves to illustrate the concept that the execution time of SQL is heavily dependent on the way a query is stated, as well as the internal index structures within Oracle. It’s true that each dialect of SQL is different, but general rules apply that can be used to keep database queries running efficiently. And while these guidelines are no substitute for the SQL explain plan facility, they can reduce the chances that a database query will consume large amounts of system resources. The first step is to look at the relative costs for each type of SQL access. Oracle has published the cost list shown in Table 17.1 that describes the relative cost of each type of SQL access. Table 17.1Costs for SQL access. Cost<br />
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Type of Operation<br />
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1<br />
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Single row by row ID (rowid)<br />
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2<br />
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Single row by cluster join<br />
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3<br />
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Single row by hash cluster key with unique or primary key<br />
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4<br />
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Single row by unique or primary key<br />
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5<br />
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Cluster join<br />
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6<br />
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Hash cluster key<br />
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7<br />
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Indexed cluster key<br />
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8<br />
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Use of a multicolumn index<br />
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9<br />
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Use of a single-column index<br />
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10<br />
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Bounded range search on indexed columns<br />
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11<br />
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Unbounded range search on unindexed columns<br />
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12<br />
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Sort-merge join<br />
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13<br />
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Max or min search of an indexed column<br />
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14<br />
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Use of order by on an indexed column<br />
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15<br />
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Full-table scan<br />
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As you can see, the fastest way to retrieve a row is by knowing its row ID. A row ID (called a rowid in Oracle) is the number of the database block followed by the displacement, or position, of the row on the block. For example, 1221:3 refers to the third row on a page, on block number 1221. Many experienced Oracle programmers capture the rowid for a row if they plan to re-retrieve it. In Oracle, rowid is a valid column statement, such that you can select the rowid along with your data in a single statement, such as: select rowid from EMPLOYEE into :myvar; Inside a WebServer application, PL/SQL storage arrays can be defined to hold rowid values. For details, see Chapter 8, WebServer’s OWA Utilities. When creating WebServer applications, keep in mind that the most expensive SQL statement is one that invokes a full-table scan. As you may know, a full-table scan is acceptable for small tables, but it can wreak havoc on an entire Oracle instance when a full-table scan is invoked against a large table. Therefore, more than any other SQL tuning technique, avoiding large-table full-table scans is a primary consideration. With proper tuning of Oracle SQL, full-table scans can usually be avoided by using indexes and index hints. What about queries that need to read every row of a table? While a full-table scan may be the fastest for an individual query where every row in the table must be read (i.e., using sum, avg, or queries with many complex where conditions), the full-table scan is done at the expense of other SQL on the system. As a large-table full-table scan reads rows into memory, buffer pages containing rows from other queries will be flushed from the buffer, and Oracle will need to re-retrieve these rows. So, the question is, do you tune an individual query for performance, or do you tune the database as a whole? Generally speaking, we cannot allow a single query to achieve good response time at the expense of all other tasks on the database.<br />
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General Tips For Efficient SQL Fortunately, some general rules are available for writing efficient SQL in Oracle. These rules may seem simplistic, but diligently following them will relieve more than half of your SQL tuning problems. • Never do a calculation on an indexed column (e.g., where salary*5 > :myvalue). • Whenever possible, use the union statement instead of or. • Avoid the use of not in or having in the where clause. Instead, use the not exists clause. • Always specify numeric values in numeric form and character values in character form (e.g., where emp_number = 565, where emp_name = ‘Jones’). • Avoid specifying NULL on an indexed column. • Avoid the like parameter if = will suffice. Using any Oracle functions will invalidate the index, causing a full-table scan. • Never mix datatypes in Oracle queries, as it will invalidate the index. If the column is numeric, remember not to use quotes (e.g., salary = 50000). For char index columns, always use quotes (e.g., name = ‘BURLESON’). • Remember that Oracle’s rule-based optimizer looks at the order of table names in the from clause to determine the driving table. Always make sure that the last table specified in the from clause is the table that will return the smallest number of rows. In other words, specify multiple tables with the largest result set table specified first in the where clause. • Avoid using subqueries when a join will do the job. • Use the Oracle decode function to minimize the number of times a table has to be selected. • To turn off an index you do not want to use (only with cost-based), concatenate a<br />
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null string to the index column name (e.g., name||‘’), or add zero to a numeric column name (e.g., salary+0). • If your query will return more than 20 percent of the rows in the table, use a fulltable scan rather than an index scan. • Always use table aliases when referencing columns. Historically, queries pose a common problem with SQL. Simple queries can be written in many different ways, each variant of the query producing the same result but with widely different access methods and query speeds. For example, a simple query such as “What students received an A last semester?” can be written in three ways, as shown in Listings 17.1, 17.2, and 17.3, each returning an identical result. Listing 17.1 A standard join. select * from STUDENT, REGISTRATION where STUDENT.student_id = REGISTRATION.student_id and REGISTRATION.grade = 'A'; Listing 17.2 A nested query. select * from STUDENT where student_id = (select student_id from REGISTRATION where grade = 'A' ); Listing 17.3 A correlated subquery. select * from STUDENT where 0 < (select count(*) from REGISTRATION where grade = 'A' and student_id = STUDENT.student_id ); Each of these queries will return identical results, but the access path that the queries take through the Oracle database varies greatly.<br />
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The following discussion will review the basic components of an SQL query, showing how to optimize a query for remote execution. It is important to note that several steps are required to understand how SQL is used in a distributed database. Distributed SQL queries function in the same way as queries within a single database, with the exception that crossdatabase joins and updates may utilize indexes that reside on different databases. Regardless, a basic understanding of the behavior of SQL can lead to dramatic performance improvements.<br />
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Using Oracle’s Explain Plan Facility Because SQL is a declarative language, it is not immediately apparent how an SQL query is being serviced. Whether or not Oracle is using an index, performing a full-table scan, or performing a merge sort, is hidden from view. Fortunately, tools exist within Oracle’s implementation of SQL that allow the access path to be interrogated. To see the output of an explain plan, you must first create a plan table to store the output from the explain. Oracle provides a script in $ORACLE_HOME/rdbms/admin with a script called utlxplan.sql. Execute utlxplan.sql, and create a public synonym for the PLAN_TABLE, as follows: sqlplus>@utlxplan table created. sqlplus > create public synonym PLAN_TABLE for SYS.PLAN_TABLE; synonym created. Oracle uses the explain utility by taking the SQL statement as input, running the SQL optimizer, and then sending the access path information into a PLAN_TABLE, which can then be interrogated to see the access methods. Listing 17.4 runs a query against a sales database to get the sum of costs for a particular month. Listing 17.4 A database query against a sales database. explain plan set statement_id = 'test1' for set statement_id = 'run1' into PLAN_TABLE for select 'T'||costsnet.terr_code, 'P'||detcost.pac1 || detcost.pac2 || detcost.pac3, 'P1', sum(costsnet.ytd_d_ly_tm), sum(costsnet.ytd_d_ty_tm), sum(costsnet.jan_d_ly), sum(costsnet.jan_d_ty), from costsnet, detcost where costsnet.mgc = detcost.mktgpm and detcost.pac1 in ('N33','192','195','201','BAI', 'P51','Q27','180','181','183','184','186','188', '198','204','207','209','211') group by 'T'||costsnet.terr_code, file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/528-532.html (3 of 4)4/03/2005 6:16:47<br />
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'P'||detcost.pac1 || detcost.pac2 || detcost.pac3; This syntax is piped into the SQL optimizer, which will analyze the query and store the plan information in a row in the plan table identified by RUN1. Please note that the query will not execute; it will only create the internal access information in the plan table. The plan table contains the following fields: • operation—Type of access being performed. Usually table access, table merge, sort, or index operation. • options—Modifiers to the operation, specifying a full table, a range table, or a join. • object_name—Name of the table being used by the query component. • process ID—Identifier for the query component. • parent ID—Parent of the query component. Note that several query components may have the same parent.<br />
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Now that the PLAN_TABLE has been created and populated, you may interrogate it to see your output by running the following query: rem plan.sql - displays contents of the explain plan table set pages 9999; select lpad(' ',2*(level-1))||operation operation, options, object_name, position from plan_table start with id=0 and statement_id = 'RUN1' connect by prior id = parent_id and statement_id = 'RUN1'; Listing 17.5 shows the output from the plan table. Listing 17.5 The plan table’s output. SQL>@list_explain_plan OPERATION ——————————————————————————————————— OPTIONS OBJECT_NAME ————————————— ——————————————— SELECT STATEMENT SORT GROUP BY<br />
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POSITION ————————————<br />
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CONCATENATION 1 NESTED LOOPS TABLE ACCESS FULL<br />
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COSTSNET<br />
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1 1<br />
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TABLE ACCESS BY ROWID<br />
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DETCOST<br />
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2<br />
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INDEX RANGE SCAN<br />
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DETCOST_INDEX5<br />
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1<br />
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NESTED LOOPS From this output, you can see the dreaded table access full on the COSTSNET table. To diagnose the reason, return to the SQL and look for any COSTSNET columns in the where clause. There you can see that the COSTSNET column called mgc is being used as a join column in the query, indicating that an index is necessary on COSTSNET.mgc to alleviate the full-table scan. While the plan table is useful for determining the access path to the data, it doesn’t tell the whole story. The configuration of the data is also a consideration. While the SQL optimizer is aware of the number of rows in each table (the cardinality) and the presence of indexes on fields, the SQL optimizer is not aware of data distribution factors, such as the number of expected rows returned from each query component. The other tool used with the plan table is an SQL trace facility. Most database management systems provide a trace facility that shows the resources consumed within each query component. The trace table will show the number of I/Os required to perform the SQL, as well as the processor time for each query component. Some other relational databases, such as DB2, allow the DBA to specify the physical sequence for storing the rows. Generally, this sequence will correspond to the column value most commonly used when the table is read sequentially by an application. If a customer table is frequently accessed in customer ID order, then the rows should be physically stored in customer ID sequence. The explain plan output will display many database access methods. The major access techniques include: • and-equal—Indicates that tables are being joined and that Oracle will be able to use the values from the indexes to join the rows. • concatenation—Indicates an SQL union operation. • counting—Indicates the use of the SQL count function. • filter—Indicates that the where clause is removing unwanted rows from the result set. • first row—Indicates that a cursor has been declared for the query. • for update—Indicates that returned rows were write locked (usually by using the select…for update of…). • index (unique)—Indicates that an index was scanned for a value specified in the where clause. • index (range scan)—Indicates that a numeric index was scanned for a range of values (usually with the between, less_than, or greater_than specified). • intersection—Indicates a solution set from two joined tables. • merge join—Indicates that two result sets were used to resolve the query. • nested loops—Indicates that the last operation will be performed n times, once for each preceding operation. For example, below the index (unique), these operations will be performed for each row returned by table access (full): nested loops, table access (full) of ‘customer’, and index (unique) of sy_01_idx. • projection—Indicates that only certain columns from a selected row are to be returned. • sort—Indicates a sort, either into memory or the TEMP tablespace. • table access (rowid)—Indicates a row access by rowid that is very fast. • table access (full)—Indicates a full-table scan and is usually cause for concern unless the<br />
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table is very small. • union—Indicates that the distinct SQL clause was probably used. • view—Indicates that an SQL view was involved in the query. Database statistics packages can be made to capture this information, but they tend to be very resource intensive. Turning on SQL trace statistics for a very short period of time during processing is a good practice to follow and enables you to gather a representative sample of the SQL access. Using Temporary Tables The prudent use of temporary tables can dramatically improve WebServer performance. Consider the following example. You want to identify all users who exist within Oracle, but have not been granted a role. You could formulate the following query: select username from dba_users where username not in (select grantee from dba_role_privs); This query runs in 18 seconds. Now, you could rewrite the same query to utilize temporary tables, as follows: create table temp1 as select distinct username from dba_users; create table temp2 as select distinct grantee from dba_role_privs; select username from temp1 where username not in (select grantee from temp2); This query runs in less than 3 seconds.<br />
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Tuning With The Rule-Based Optimizer In Oracle’s rule-based optimizer, the ordering of the table names in the from clause determines the driving table. The driving table is important because it is retrieved first, and the rows from the second table are then merged into the result set from the first table. Therefore, it is essential that the second table returns the least amount of rows based on the where clause. This is not always the table with the least amount of rows (i.e., the smallest cardinality). For example, consider two EMP_TABLEs—one in London and another in New York, as shown in Table 17.2. Table 17.2New York and London EMP_TABLES. Rows<br />
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Dpt 100<br />
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New York<br />
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1,000<br />
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100<br />
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900<br />
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London<br />
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200<br />
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150<br />
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50<br />
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In this example, a total select from the EMP_TABLE should specify the New York table first because London has the least amount of returned rows. The SQL should appear as follows: select * from emp@new_york, emp@london; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/535-539.html (1 of 4)4/03/2005 6:16:49<br />
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If the SQL specifies a where condition to include only Department 100, the order of table names should be reversed, as follows: select * from emp@london, emp@new_york where DEPT = 100; It’s not always known what table will return the least amount of rows, so procedural code could be used to interrogate the tables and specify the tables in their proper order. This type of SQL generation can be very useful for ensuring optimal database performance, as shown in Listing 17.6. Listing 17.6 Automatic generation of optimal rule-based SQL. select count(*) into :my_london_dept from emp@london where dept = :my_dept; select count(*) into :my_ny_dept from emp@new_york where dept = :my_dept; if my_london_dept >= my_ny_dept { table_1 = emp@london table_2 = emp@new_york else table_1 = emp@new_york table_2 = emp@london } /* Now we construct the SQL */ select * from :table_1, :table_2 where dept = :my_dept; As you probably know, Oracle version 7 offers two methods of tuning SQL. If you are running version 7.2 or above, you can use the cost-based optimizer; releases of Oracle 7.1 and below require the rule-based optimizer. With the rule-based optimizer, the indexing of tables and order of clauses within an SQL statement control the access path. The cost-based optimizer automatically determines the most efficient execution path, and the programmer is given hints that can be added to the query to alter the access path. The cost-based optimizer or the rule-based optimizer is set in the init.ora file when the DBA sets the optimizer_mode to rule, choose, first_rows, or all_rows. Beware of using the choose option. When you give Oracle the ability to choose the optimizer mode, Oracle will favor the cost-based approach if any of the tables in the<br />
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query contains statistics. (Statistics are created with the analyze table command.) For example, if a three-table join is specified in choose mode and statistics exist for one of the three tables, Oracle will decide to use the cost-based optimizer and will issue an analyze table estimate statistics at runtime. This will dramatically slow down the query. The optimizer option (rule versus cost) can be controlled at the database level or at the program level. Prior to version 7.0.16, the cost-based analyzer had significant problems, and Oracle recommended the use of the rule-based optimizer. Here are some tips for effective use of Oracle’s rule-based optimizer: • Try changing the order of the tables listed in the from clause. Page 1915 in Oracle RDBMS Database Administrator’s Guide states, “Joins should be driven from tables returning fewer rows rather than tables returning more rows.” In other words, the table that returns the fewest rows should be listed last. This usually means that the table with the most rows is listed first. If the tables in the statement have indexes, the driving table is determined by the indexes. One Oracle developer recently slashed processing time in half by changing the order of the tables in the from clause. Another developer had a process shift from running for 12 hours to completing in 30 minutes by changing the from clause. • Try changing the order of the statements in the where clause. Here’s the idea: Assume that an SQL query contains an if statement with several boolean expressions separated by ands. Oracle parses the SQL from the bottom of the SQL statement in reverse order. Therefore, the most restrictive boolean expression should be on the bottom. For example, consider the following query: select last_name from STUDENT where eye_color = 'BLUE' and national_origin = 'SWEDEN';<br />
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Here, the number of students from Sweden is assumed to be smaller than the number of students with blue eyes. To further confound matters, if an SQL statement contains a compound if separated by ors, the rule-based optimizer parses from the top of the where clause. Therefore, the most restrictive clause should be the first boolean item in the if statement. • Analyze the existence/nonexistence of indexes; understand your data. Again, unlike the cost-based optimizer, the rule-based optimizer only recognizes the existence of indexes and does not know about the selectivity or the distribution of the index column. Consequently, use care when creating indexes, especially when using rule-based optimization. Consider all programs that use a field in a where clause of a select. A field should only be indexed when a very small subset (less than 10 percent) of the data will be returned. • Check to see if the target table is fragmented. For example, a table could be fragmented if it constantly has a large number of rows inserted and deleted. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/535-539.html (3 of 4)4/03/2005 6:16:49<br />
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This is especially true in pctfree because the table has been set to a low number. Regular compression of the table with Oracle’s export/import utility will restore the table row and remove fragmentation. • Always run questionable SQL through explain plan to examine the access path. • Understand which “query paths” are the fastest. For example, accessing a table by rowid is the fastest access method available where a full-table scan is 17 out of 18 for the ranking of query paths. (Reference Table 17.1 for the complete list of relative costs.) • Avoid joins that use database links into Oracle version 6 tables. • Make effective use of arrays. Array processing significantly reduces database I/O. Consider the following example. A table has 1,000 rows to be selected. The records are manipulated and then updated in the database. Without using array processing, the database receives 1,000 reads and 1,000 updates. With array processing (assuming an array size of 100), the database receives 10 reads (1,000/100) and 10 updates. According to Oracle, increasing the array size to more than 100 has little benefit. Beware of an Oracle rule-based “feature” whereby a join of numerous large tables will always result in a full-table scan on one of the tables, even if all of the tables have indexes and the join could be achieved with an index scan. Of course, full-table scans are costly, and SQL hints can be used to force the query to use the indexes. You can use hints with the rule-based optimizer.<br />
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Using Hints With The Cost-Based Optimizer The rule-based optimizer is supposed to be obsolete with the introduction of Oracle version 8, but its replacement—the cost-based optimizer—is already available today. Unlike the rule-based optimizer, which uses heuristics to determine the access path, the cost-based optimizer uses data statistics to determine the most efficient way to service the request. Here is a summary of the most common hints that can be added to SQL: • all_rows—This is the cost-based approach designed to provide the best overall throughput. • cluster—Requests a cluster scan of the table(s). • first_rows—This is the cost-based approach designed to provide the best response time. • full—Requests the bypassing of indexes doing a full-table scan. • index—Requests the use of the specified index. If no index is specified, Oracle will choose the best index. • rowid—Requests a rowid scan of the specified table. • rule—Indicates that the rule-based optimizer has been invoked (sometimes to the absence of table statistics). • ordered—Requests that the tables should be joined in the order that they are specified. For example, if you know that a STATE table has only 50 rows, you may want to use this hint to make STATE the driving table. • use_nl—Requests a nested loop operation with the specified table as the driving<br />
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table. • use_merge—Requests a sort-merge operation. Remember, the cost-based optimizer will only be as accurate as the statistics computed from the tables. The DBA will need to create a periodic cron job for statistics. This job will re-estimate statistics for tables that are volatile and change columns frequently. While a full analyze table xxx estimate statistics will interrogate every row of the table, a faster method can be used by issuing analyze table estimate statistics sample nn rows. By taking a sample of the rows within the table, the statistics generation will run much faster. Keep in mind that one of the things the analyze command reviews is the selectivity and distribution of values within an index. As such, care should be taken to sample at least 100 rows from each table. Here is a test that created a set of three tables—DEPT, DEPT1, and DEPT2—each with an index on deptno and set optimizer_goal as rule in the init.ora. Listing 17.7 shows the results of the query. Listing 17.7 The results of the execution plan query. select /*+ INDEX(dept DEPT_PRIMARY_KEY) INDEX(dept2 i_dept2) INDEX(dept1 i_dept1)*/ dept.deptno, dept1.dname, dept2.loc from dept, dept1, dept2 where dept.deptno=dept1.deptno and dept1.deptno=dept2.deptno Misses in library cache during parse: 1 Optimizer hint: RULE Parsing user id: 48 (DON) Rows ——— 0 4 4 4 5 4 8 4 4 5<br />
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Execution Plan ————————————————————————— SELECT STATEMENT OPTIMIZER HINT: RULE MERGE JOIN SORT (JOIN) NESTED LOOPS INDEX (RANGE SCAN) OF 'DEPT_PRIMARY_KEY' (UNIQUE) TABLE ACCESS (BY ROWID) OF 'DEPT1' INDEX (RANGE SCAN) OF 'I_DEPT1' (NON-UNIQUE) SORT (JOIN) TABLE ACCESS (BY ROWID) OF 'DEPT2' INDEX (RANGE SCAN) OF 'I_DEPT2' (NON-UNIQUE)<br />
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Listing 17.8 shows the previous query’s results without any hints. Listing 17.8 The query results with no hints. select dept.deptno, dept1.dname, dept2.loc from dept, dept1, dept2 where dept.deptno=dept1.deptno and dept1.deptno=dept2.deptno file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/539-541.html (2 of 3)4/03/2005 6:16:49<br />
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Misses in library cache during parse: 1 Optimizer hint: RULE Parsing user id: 48 (JACK) Rows ——— 0 4 4 4 4 8 4<br />
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Execution Plan ————————————————————————— SELECT STATEMENT OPTIMIZER HINT: RULE NESTED LOOPS NESTED LOOPS TABLE ACCESS (FULL) OF 'DEPT2' TABLE ACCESS (BY ROWID) OF 'DEPT1' INDEX (RANGE SCAN) OF 'I_DEPT1' (NON-UNIQUE) INDEX (UNIQUE SCAN) OF 'DEPT_PRIMARY_KEY' (UNIQUE)<br />
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If a hint was added for the DEPT2 index, the full-table scan would be on DEPT1, and so on.<br />
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Tuning PL/SQL Procedure Language/SQL is the standard procedural language for WebServer applications. PL/ SQL is also commonly used within Oracle’s SQL*Forms application framework. But the reemergence of PL/SQL’s popularity for non-SQL*Forms applications can be attributed to the benefits of using Oracle stored procedures—which must be written with PL/SQL. It is Oracle’s stored procedures that make the htp utilities possible for WebServer implementation. PL/SQL offers the standard language constructs, including looping, if statements, assignment statements, and error handling. There are several problems with PL/SQL, each of which warrants special attention. PL/SQL offers two types of SQL cursors: the explicit cursor and the implicit cursor. Explicit cursors are manually declared in the PL/SQL, as follows: DECLARE CURSOR C1 IS select last_name from customer where cust_id = 1234; However, it’s possible to issue the SQL statement directly in PL/SQL without specifying the cursor name. When this happens, Oracle opens an implicit cursor to handle the request. Implicit cursors create a tremendous burden for Oracle, as the implicit cursor must always reissue a fetch command to ensure that only a single row is returned by the query. This will double the amount of fetch statements for the query. The moral is simple: Always declare all cursors in your PL/ SQL. PL/SQL allows certain types of correlated subqueries to run much faster than traditional Oracle<br />
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SQL queries. This is a critical issue with WebServer, because it may be much faster to embed all Oracle SQL in PL/SQL rather than embedding the SQL in Perl or Java. To illustrate why WebServer may run faster with PL/SQL than with Perl or Java SQL, consider a situation where a bank maintains a general ledger table and a transaction table. At the end of the banking day, the check transaction table is applied to the GENERAL_LEDGER table, making the requisite deductions from the account_balance column. Let’s assume that the GENERAL_LEDGER table contains 100,000 rows and 5,000 daily checks need to be processed. A traditional SQL query (shown in Listing 17.9) used to accomplish the updating of account_balance would involve a correlated subquery. This is the type of SQL that you might embed into a Perl or Java script for a WebServer application. Listing 17.9 Using a traditional SQL query. update general_ledger set account_balance = account_balance (select check_amount from transaction where transaction.account_number = general_ledger.account_number) where exists (select 'x' from transaction where transaction.account_number = general_ledger.account_number); When Oracle detects a correlated subquery, Oracle will execute the subquery first, and then apply the query result to the entire outer query. In this case, the inner query will execute 5,000 times, and the outer query will be executed once for each row returned from the inner query. This is called a Cartesian product and has always been a problem for this type of query. Now, consider the identical query written in PL/SQL, as shown in Listing 17.10. Listing 17.10 The PL/SQL query. DECLARE CURSOR c1 is select account_number, check_amount from transaction; keep_account_number keep_check_amount<br />
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number; number;<br />
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BEGIN OPEN C1; LOOP fetch C1 into keep_account_number, keep check_amount; exit when C1%NOTFOUND; update general_ledger set account_balance = account_balance - keep_check_amount where account_number = keep_account_number; END LOOP; file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch17/541-544.html (2 of 3)4/03/2005 6:16:50<br />
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END; Here you can see that each check amount is retrieved in a separate transaction and fetched into cursor C1. For each check_amount, the balance is applied to the GENERAL_LEDGER row, one at a time.<br />
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Summary Now that you’ve reviewed Oracle database tuning for WebServer, let’s take a look into the future to get an idea how the nature will be changing. As you may know, the next major release of Oracle (version 8) will have object-oriented features, and the WebServer developer will benefit from understanding how these changes to the Oracle architecture will affect the Oracle WebServer product.<br />
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CHAPTER 18 The Future Of Database Management While Oracle WebServer is considered cutting-edge technology today, it will only be a few short years before the technology again shifts direction. The introduction of Oracle version 8, the concept of a “universal” database server, and the advances in hardware technology are combining to present an exciting future for Oracle applications. Many new terms are being used to describe future database systems—knowledgebases, intelligent databases, neural databases, and database machines are but a few. Oracle version 8 is just the beginning.<br />
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Oracle Version 8 The next progression of database architectures is moving toward object-oriented databases. Early file managers stored data; network databases stored data and relationships; object-oriented databases will store data, data relationships, and the behaviors of the data. In general, the Oracle8 engine is remarkably similar to the relational engine found in Oracle 7.3, but with major extensions to the relational architecture. It is interesting to note that Oracle has not discarded the idea of creating a “universal” database engine. Oracle is calling Oracle8 the “Oracle Universal Server,” adding text and multidimensional and object capabilities to the relational engine. The most exciting enhancements involve the introduction of Sedona, the incorporation of the Oracle file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch18/545-548.html (1 of 3)4/03/2005 6:16:51<br />
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Express MDDB, and the “object layer” that will be tightly coupled with the relational engine. Oracle Sedona Due to the secrecy around the development of Oracle8, many Oracle professionals assumed that Sedona was the code name for Oracle8. However, Sedona is actually an extension to Oracle8. Sedona has been billed as a universal object manager, and it appears that its basic function is to act as an object consolidator. Sedona will allow for Oracle methods to be indexed and quickly located across many databases and platforms. Sedona achieves this by placing an object wrapper around Oracle objects so that they can be accessed by other distributed systems. While the details are sketchy, Sedona will incorporate many of the features of an Object Request Broker (ORB), with a metadata dictionary for the distributed management of objects. With Sedona, object classes may be registered in a central repository so that they will be available for use transparently across the enterprise. Oracle has made the interface specifications for Sedona available to third-party software vendors, hoping that vendors will create application products utilizing Sedona. Oracle ConText A text searching option called Oracle ConText has also been added to the relational engine of Oracle8. Oracle ConText allows thematic word searching capabilities against Oracle’s relational database. Although the ConText option indexes on each word within the text, the real power of the text retrieval system is located in the frontend software. While this represents a major improvement over Oracle Book (which is now obsolete), it remains to be seen how ConText will compete in the marketplace as a text search engine. There are two fundamental ways to measure the accuracy of text retrieval: • Precision—Retrieves only relevant documents (no false or “noisy” hits). • Recall—Retrieves all relevant documents in a given data collection. Together, precision and recall represent the overall accuracy of a text retrieval system. Natural language is a phrase frequently heard in conjunction with concept-based searching, and morphology is a term commonly used by text databases to simulate natural language query. Morphology recognizes basic units of meaning and parts of speech. To understand morphology, consider the phrase “Please write to Mr. Wright right now.” To the human ear, all of the words sound identical; the meaning of the words can be determined only by the context of the sentence. From the initial review, it is still unclear how well Oracle ConText will be able to compete with the other more established text engines such as ConQuest, Fulcrum, and Folio. Oracle Express Unlike Oracle 7.3, where the Express multidimensional database was installed independently of Oracle, the Express product has been incorporated into the Oracle8 kernel. This implies yet another change for Oracle DBAs, who must now manage both the relational and multidimensional components of Oracle. Oracle Express will be offered for NT and PC, as well as Unix platforms. The basic reporting functions of<br />
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Express have been enhanced to provide forecasting and model building. Unlike the Express product developed by IRI, Oracle Express has been enhanced so that it does not require data to be preloaded into its internal data structures. This enhancement enables Express to read relational data directly from relational Oracle databases, dynamically transforming and aggregating the data for multidimensional presentation. This means that Express will now compete against other relational backend products, such as Holos and MetaCube. SQL For Object-Orientation The object-oriented approach borrows heavily from C++ and Smalltalk. Both languages allow for the storing of behaviors with the data, such that data and business rules share a common repository. With the properties of encapsulation, abstraction, and polymorphism, object technology systems are moving toward a unified data model that models the real world far more effectively than previous modeling techniques. Furthermore, a properly designed object-oriented model promises to be maintenance-free, because all changes to data attributes and behaviors become a database task—not a programming task. The distinguishing characteristic of the object-oriented database is its ability to store data behavior. At first glance, incorporating data into the database may seem to be a method for moving application code from a program into a database. While it is true that an object-oriented database stores behaviors, these databases must also have the ability to manage many different objects—each with different data items.<br />
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The ISA Relationship As presented earlier in this book, the ISA relationship is a data relationship that indicates a type/subtype data relationship. While traditional E/R modeling deals only with single entities, the ISA approach recognizes that many “types” or classes of an individual entity may exist. In fact, the ISA relationship is the foundation of objectoriented programming, which allows the designer to create hierarchies of related classes and then use inheritance and polymorphism to control which data items will participate in the low-level objects. Oracle is planning to introduce an extension to their Designer/2000 product to allow for the modeling of class hierarchies. This new extension, tentatively dubbed Designer/2001, should allow for object-oriented constructs to be described and modeled.<br />
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The ODMG Object Model ODMG is a vendor organization dedicated to providing standards for object-oriented databases. The ODMG object model was developed jointly by a consortium of objectoriented database vendors. These companies feel a sense of urgency to create a unified standard for object-oriented databases, and they have prepared the ODMG model in the hope that all OODB vendors will adopt the model. Current commercial OODB systems are not portable across hardware platforms, and it is hoped that a joint approach toward object-oriented database architecture will create an environment where object-oriented systems share many characteristics, just as relational databases file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch18/548-551.html (1 of 3)4/03/2005 6:16:51<br />
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share common interfaces, such as SQL. Because of a lack of standards for object-oriented database architectures, most of the major OODB vendors have been creating commercial products with very diverse internal structures. A recent effort has been made to propose a standard architecture for object-oriented database systems (Loomis, 1993), and this standard may become the foundation for an industry-wide architecture for object-oriented databases. The ODMG object model was developed jointly by a consortium of object-oriented database vendors, including Versant, Ontos, O2 Technology, Object Design, SunSoft, and Objectivity corporations. Notably absent is Microsoft. While we can only speculate about Microsoft’s failure to participate in these standards, their market dominance may have something to do with their level of participation. The other companies feel a sense of urgency in creating a unified standard for object-oriented databases, and they have prepared the ODMG model in the hope that all OODB vendors will adopt the model. The ODMG model creates an independent model that is language independent, and object models may be bound to many different languages. ODMG develops a hierarchy of objects with the most general object called a denotable object. Denotable objects may be mutable or immutable. A mutable object may change its values and properties, but an immutable object contains only literal values. Within immutable objects, we find two subcategories: atomic and structured (as shown in Figure 18.1). A denotable, immutable, atomic object is represented by the same datatypes found in relational databases, namely char, integer, and float. A denotable, immutable, structured object is a literal structure such as the date and time datatypes.<br />
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Figure 18.1 The ODMG object model. Unlike the relational database model, the ODMG model requires that all objects are assigned an object identifier (OID) to uniquely identify each object. While still unclear, it appears that it is not possible to reference an object by the data values in the object. For example, in a relational database, one could state select * from order where order_nbr = 123; this would not be possible under the current ODMG object model. Rather, the ODMG model requires database currency to locate the object, and the system must know the OID. The ODMG model also categorizes objects according to their lifetime within the runtime system. Temporary objects, those associated with a procedure or a process, are classified separately from database objects, which require external storage. The ODMG object model also attempts to redefine the basic principles of entity/ relationship modeling, but carries the concept one step further, specifying directionality when navigating the data relationship. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/ch18/548-551.html (2 of 3)4/03/2005 6:16:51<br />
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This model also specifies navigational operators to traverse the linked-list data structures found in commercial implementations of object-oriented databases. These operators are remarkably similar to the DML found in other pointer-based models, such as CODASYL, and include verbs such as create, add_member, and traverse. The model also has database operators that help maintain data integrity. These are absolutely identical to the CODASYL network data model and have the verbs begin, commit, abort, and checkpoint. ODMG attempts to recognize the importance of coexistence with relational databases, and the ODMG model is called a superset of the relational database model. The ODMG authors state: An important difference between the relational model and the ODMG object model is that the relational model does not support user-defined subtyping of the type hierarchy. Only built-in types can be used by applications. An object programmer must translate objects into the predefined structures supported by the relational DBMS in order to use the relational DBMS for persistent storage. Only the predefined, tableoriented operations supplied by SQL can be used to access the relational database. By contrast, the ODMG object model provides a way for application semantics to be expressed explicitly in the schema and supported directly by the OODBMS. (Loomis, 1993)<br />
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The Future Of Hypermedia In Database Management Hypermedia has become a very popular term within the arena of database systems. Many PC-based systems and products advertise themselves as “hypermedia,” but a comparison of these products shows that they have very little in common. In basic terms, hypermedia refers to the ability of the database to incorporate audio and video information. From a database perspective, this audio and video information is simply other sources, or media. Many databases already allow for the inclusion of graphical images, and even mainframe databases allow for Binary Large Object (BLOB) datatypes. The latest craze within PC-based systems is the inclusion of WAV files. These files consist of binary audio information and always have the .WAV suffix, such as HORN. WAV. These files create predetermined sound effects and can be triggered by events within the system. For example, Microsoft Windows uses video-clip files, which allow for the inclusion of moving videos within the database. Many flashy database systems have been created by the addition of audio and video, and Microsoft corporation implements OLE (pronounced Oh-Lay), which refers to their Object Linking and Embedding technology. From a database perspective, these new forms of information are not a problem for the database designer. Sound effects and moving images are stored in the database and<br />
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retrieved on request, just like conventional information. The problem with hypermedia lies in the effective design and presentation of the hypermedia information. Microsoft’s OLE allows divergent media to be incorporated into a single application. OLE runs under Microsoft Windows and allows a user to bundle audio, video, and graphics from any source in the Windows domain. Hyper in the phrase hypermedia system refers to the ability of the system to allow links, or calls, to other components within the system that contain ancillary information. These hyperlinks are commonly used within the Windows environment and allow the user of the system to dynamically move to other areas of interest. This concept is analogous to the See also references within encyclopedias. Some text-based databases, such as the Folio database, allow for linking between textual items. The real problem with the development of hypermedia systems is the presentation style of the system. Many vendors create hypermedia shells that allow database designers to add hypertext links to their applications, and it is very simple for a novice to create a system that takes advantage of sound and video. Unfortunately, many of these systems suffer from an artistic overload. Data processing professionals often have trouble with the feel for the dynamics of an effective presentation system, and the delivered products are often “noisy” and distracting. Today, the development of hypermedia systems should be done by professional choreographers who use design techniques more familiar to advertising professionals than computer programmers. This has major implications for the future of database systems design. The tools for the presentation of material are now so sophisticated that anyone can develop a hypermedia system, but not everyone can create an effective user interface. In many areas of database design, a feel for artistic design and graphics presentation will be more important than technical skills.<br />
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A Return To Centralized Data As corporations begin to realize that widespread distribution of their data resources can cause severe problems, there will be a movement toward the data warehouse concept (see Figure 18.2). Just as we saw a movement towards centralized data repositories in the 1970s, we are now seeing the same type of movement as a result of the failure of distributed data mechanisms to provide a simple solution to corporatewide data. This is not a condemnation of the replication tools within Oracle databases but simply a backlash against the inherent complexity involved when distributing data across multiple physical locations.<br />
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Figure 18.2 The return to centralized databases. From a data management viewpoint, the same problems that led to the invention of the first commercial databases are now returning. Thirty years ago, the industry was in the age of departmental computing, whereby each area within an organization had its own<br />
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data processing staff, its own systems, and worst of all, its own data and data structures. This lack of data sharing is now returning as more departments are abandoning the mainframe and developing their own systems on PC platforms or midrange computers. You should remember that the impetus behind downsizing is primarily monetary. There is no reason to migrate from a mainframe to smaller systems except for the cheaper MIPS available on the smaller machines. Unfortunately, many companies are not only distributing their processing, they are distributing their data, often with disastrous results. As more and more companies learn that distributing their data can cause problems at the corporate level, we will see a move toward the recentralization of data. This doesn’t mean a return to the mainframe as we know it; it means that very large amounts of data will be managed and distributed to all platforms within a company.<br />
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Experiential Databases As the cost of computer hardware continues to fall, data processing will undergo another revolution. Just as the first supercomputers went unnoticed by mainstream computer professionals, the new hardware technology will emerge with a whisper. However, the implications toward the way people think about databases will change dramatically. Peripheral sensors have been developed that are far superior to human peripherals, but cognitive development lags far behind. We have cameras that can read a newspaper headline from outer space and ears that can hear far better than our own, but we have never mastered the cognitive ability of even the most primitive animal. Every second, the human mind processes thousands of bits of information. We perceive the distant humming of fluorescent light bulbs, the pressure of our bodies against our chairs, and many other perceptions unnoticed by our conscious mind. Numerous researchers in human cognition hypothesize that the human mind never forgets; what is lost when a memory is forgotten is the ability to recall the data and not the data itself. Oliver Sacks, the famous brain surgeon portrayed in the movie Awakenings, related a story in his fascinating book, The Man Who Mistook His Wife For A Hat. Doctor Sacks was performing brain surgery on a conscious patient when stimulation to a specific area of the brain caused the patient to remember a long forgotten incident. Remembering is not really an appropriate term, because the patient relived the incident and described a scene from her childhood in such detail that she could sing along with a tune playing on the Victrola.<br />
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When computers advance to the point where storage capacity approaches the capacity of the human mind, there will be a movement toward experiential database machines. Experiential machines will perceive the world around them and process information in a similar fashion to the human mind. Computers have long been able to learn from experience. Early database experiments in the 1960s demonstrated that a naive computer could learn the rules to simple games by playing the game with another computer. However, human reasoning often differs from computer reasoning—often in very fundamental ways. An excellent example happened during World War II when the allied forces were planning bombing raids on Germany. Attempts at bombing targets in Germany had proved disastrous, with well over onehalf of the aircraft lost. A primitive computer was engaged to solve the problem of delivering the maximum bomb load while minimizing the amount of lives lost. The computer was able to prove that less lives would be lost if a smaller number of planes were sent on the missions. Each of these planes would carry double the bomb load and just enough fuel to reach their target. After dropping their bombs, the crew would bail out and take their chances within Axis territory. Assume, for the point of this argument, that the statistical conclusion was correct, and that less lives would be lost if these one-way trips were adopted. The members in the Eighth Air Force were somewhat less than elated with this proposed solution, and elected to ignore the study. The idea of drawing straws for oneway trips to Germany was abhorrent to the crew members, even though they had a much higher probability of survival. Ultimately, the air crews decided to ignore the study, and hundreds of American lives were lost as a direct result of “irrational” human cognition. An experiential system needs to be able to perceive and act upon stimuli in the world. In order to do so, a model would need to be developed that would allow the database to retain information in a similar fashion to the human mind. Sigmund Freud postulated that human memory is persistent. All memories are retained within the brain, but most are inaccessible. These inaccessible, or unconscious, memories and experiences are nonetheless present and serve to guide the decision-making abilities of the human organism. Other psychologists have postulated that the human mind has very little ability to address detailed memory, and the human mind filters out unneeded stimuli, storing only what is required for the organism. This filtering mechanism is activated by priorities set by the conscious mind. For example, a pessimist chooses to ignore positive stimuli and instead focuses on the bad events of the day. Emotional reactions also govern what is stored in the mind. The human mind represses, or blocks, events that are unacceptable to the conscious mind, and would therefore interrupt the functioning of the organism. These types of filtering devices will need to be incorporated into the database memory processors, and a great deal will be learned about the relationship between human and computer cognition.<br />
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Voice Recognition Database Access Recognizing a human voice is one of the first things a baby learns, but it’s a very complex skill for a computer to learn. To create a system with voice recognition, a method needs to be devised that will allow voice access to database managers. Unfortunately, computers have had dismal results when learning to parse and understand human English. It is relatively simple to digitize sound waves for processing by a computer, but it is very difficult to get a computer to partition the sounds into words and to recognize where words begin and end. For example, computers have a hard time recognizing that bus station is two words because the sounds run together when they are spoken. Another problem with voice recognition is context-sensitive grammar. Even a child understands what it means when someone says, “Mary had a little lamb.” A computer, on the other hand, will be unable to resolve the verb had. What do you mean Mary had a little lamb? Did she buy the lamb? Did she eat the lamb? Exactly how did she have this lamb? Determining the context of spoken English has been a difficult, but not insurmountable task. Technology has progressed to the point where computers can isolate individual spoken words and can spell the words according to their context, such as “please write to Mr. Wright, right now.” After the spoken words and their individual meanings have been determined, the next step is to derive the meaning from the sentence. Nonstructured access to databases has<br />
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long been of interest to researchers, and several products have come to the marketplace. Computer Associates markets a product called Online English, which claims to allow nonstructured queries against their IDMS database product. Other vendors have created tools that allow macros for the classification of database queries. For example, a user could state, “All salesmen who have not sold 3,000 products this month are turkeys.” This establishes a condition set for the word turkey, and a subsequent query, “Show me the turkeys,” will produce a list of salesmen who have sold less than 3,000 birds. Some of this research deals with the translation of English into foreign languages. A tool was built that translates English into Russian, and a reverse component was designed to translate Russian into English. The individual components worked relatively well when presented with well-structured sentences, but more obtuse sentences produces humorous results. For example, the phrase The spirit is willing but the flesh is weak, was translated into Russian, and then back into English. When the translation was complete, the phrase said, The vodka is good, but the meat is rotten. Savvy, a database query product by Excalibur corporation, performs in the same fashion. For example, an employee database could be queried with the statement, “How long has Joe been with us?” Savvy will respond by stating, “Are you asking for Joe’s date of birth, or Joe’s date of hire?” West publishing company has recently released a tool called Natural, which provides nonstructured queries against its vast legal database. West claims that the researcher only needs to state a general concept, and Natural will create a structured query on behalf of the user, returning the desired information. Query By Example (QBE) is a database retrieval tool by IBM that allows users to query their tables without learning SQL. Users of the DB2 database are presented with a list of database fields that they can combine to create “sample” tables that contain all of the columns and rows they desire. The user could also specify selection constraints. QBE will generate the appropriate SQL for the use and return of their query in a tabular format. Despite the primitive state of today’s technology, the next 30 years will see a revolution in ad hoc database access. Tools will be devised allowing users to state a query to an intelligent front end that will parse the meaning from the statement and return the results.<br />
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Summary While this chapter may seem futuristic, many of the topics discussed will soon become commonplace within the world of database management. It remains to be seen how soon the technology will be changing, but if the current trends in hardware technology continue, it will not be uncommon to see desktop computers with enough hardware resources to make artificial intelligence a reality.<br />
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(Publisher: The Coriolis Group) Author(s): Robert Papaj and Donald K. Burleson ISBN: 1576100995 Publication Date: 02/01/97 Search this book: Go!<br />
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Index A Abstract data typing. See ADT. Abstraction, 20, 547 Access privileges types, 346 Adding redundancy issues, 461 Adobe PageMill, 46 ADT, 18, 395 Advanced Research Projects Administration Network. See ARPANET. Amigo, 394 Analysis top-down, 138 traditional systems vs. Web-page systems, 138 API, 5, 36, 160, 389, 402 AppleScript, 153, 154 Applets, 41, 391, 402, 403, 406 Application developers, cardinal rule, 144 front-ends, designing, 137 object-oriented, 26 protocol interfaces. See APIs. standalone, 5<br />
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Archie, 5 ARPANET, 1 Array, 539 associative, 307 Audio, 46, 155 Audit script, using, 368<br />
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B Basic, 24 Basic Mapping System. See BMS. Behaviors, 396 Berners-Lee, Tim, 7 BIF, 291 Bill-of-Materials explosion, 466 relationships. See BOM relationships. Binary Large Object. See BLOB. Bitmap. See BMP. Black box, 26 BLOB, 551 BMP, 60 BMS, 137 Body procedures, 166 BOM relationships, 466 Bourne shell, 153. See also CGI scripts. Browser display, 127 Built-in functions. See BIF. Burleson, Donald K., 438 Bush, Vannevar, 6<br />
<br />
C C, 154 C or C++, 153 C programming languages, 394 C++, 15, 42, 154, 392, 547. See also Languages, object-oriented. vs. Java, 395 Caillian, Robert, 7 Cartesian product, 543 Cartridge, 35 Cattributes, 45 CERN, 7 CGI, 33, 34, 36, 112, 151, 278, 405, 420, 441, 503 components, 152–59 origins, 151–52 programming, common use, 153 languages, 153 programs vs. CGI scripts, 154 scripts, 154, 159, 423 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (2 of 18)4/03/2005 6:19:55<br />
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vs. WRB, 159 Character format procedures, 169 Check constraint, 494 Checkboxes, 64, 332 Claris, 46 Class, 396 definition vs. interface definition, 400 Clickable image maps, 135, 152 Client/server, 5, 439 application, 120 architecture, 465 environment, 520 interfaces, 490 paradigm, 120 and parallelism, 497–500 processing, 120 running Java on, 402 Clones access, 122 Cluster, 519 COBOL, 14, 293 CODASYL, 15, 550 Codd, Dr. E. F., 458, 474. See also Rules of normalization. Code reusability, 395 Coherent operating system, 447 Common Gateway Interface. See CGI. Community, 439 Compiled programs vs. interpretive CGI scripts, 154 Computer Associates, 556 Concatenated index guidelines, 495 Concurrency control, 489 management, 378 Connect strings, 443 Connection client-to-server, 11 ConQuest, 118, 547 Constraints, 482 Contention, 386 Context Level DFD, 138 Cookies, 121, 251 definition, 121 expiring, 253 file, 252 Copyright, 137 Corruption, logical, 386 Cost-based optimizer. See Optimizer. Cron, 437 Crontab, 334 Cross-database access, 436 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (3 of 18)4/03/2005 6:19:55<br />
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C-shell, 147, 153, 426, 429. See also CGI scripts. Cursors types, 542 Customer ID, 127 Cyberspace domain, 143<br />
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D Data flow diagram. See DFD. Data items, 396 Data Manipulation Language. See DML. Data redundancy, 458 Data relationships many-to-many, 465–66, 519 one-to-many, 327, 460–65, 519 recursive, 466–69 types, 457 Data warehouse concept, 552 Database Administration. See DBA. Database Connection Descriptors. See DCD. Database data, 46 deadlock, 382, 385, 386, 490 experiential, 554–56 integrity, maintaining, 387 link, 432, 445, 446 locking, 382 object-oriented, 15 redundancy, 459 relationships. See Data relationships. DB2, 487, 533 DBA, 19, 20, 346, 361, 390, 547 DCD, 104, 405 Deadly embrace, 382 DEC Alpha, 395 Declare section, 292 Denotable objects, 549 Design issues major, 142 Designer 2000, 28, 548 Designer 2001, 28, 548 Developer 2000, 121 DFD, 138, 139, 140 Diagram task-flow, 141 Dictionary update running, 106 Directory list, 178 Dirty reads, 379 Displacement, 526 Distributed data file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (4 of 18)4/03/2005 6:19:55<br />
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management, 12 Distributed request, 444 Distribution, 485 DML, 15 Domain, 435 Domain name, 9 Domain Name Services, 4 Dynamic page generation, 133<br />
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E E/R model, 460, 463, 464, 465, 468, 470, 548 Effective role development guidelines, 358 Efficient SQL general tips, 528–30 Email, 5 Encapsulating code benefits, 362 Encapsulation, 26, 396, 547 vs. SQL, 27 Enquire-Within-Upon-Everything, 7 Entity/Relation model. See E/R model. Environment variables, 154 Error page generic, 323 Error statuses, 321 European Particle Physics Institute, 7 Excalibur Corporation, 557 Executables, 74, 75 Existing process, 449 Explain plan, 530 Explicit cursors, 542<br />
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F File Transfer Protocol. See FTP. Focus, 14 Folio, 118, 547 Fonts and different platforms, 122 foreign keys, redundant, 458 Form, 157, 158, 326 procedures, 169 vs. traditional online screen, 326 Fortran, 14, 153, 154 Fragments, 507 Frame, 11, 127, 167, 207 definition, 127 procedures, 167 Freud, Sigmund, 555 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (5 of 18)4/03/2005 6:19:55<br />
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FTP, 3, 5 Fulcrum, 118, 547 Full-table scans, 484, 491, 496, 518, 522, 526, 527, 539 Functional partitioning, 436 Functions, 349<br />
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G Gallium Arsenide, 15 General Interface Format. See GIF. Generalization, 28 GIF, 59, 60, 135, 337 GMT, 254, 255, 423 Gopher, 5 Gosling, James, 392 Grant privileges, cascading, 350 Graphical user interface. See GUI. GreenOS, 392 Greenwich Mean Time. See GMT. See also Time zones. GUI, 6, 8, 12, 125, 337<br />
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H Hash cluster, 517 Hashing, 516–19 Hashing algorithm, 517 Head procedures, 165 Help page, 144 Henrich, Charles, 152 High-speed phonelines, 2 Hint, 461 Holos, 547 Home Locator, 88 format, 79 Home page, 8 Horizontal partitioning, 435, 436 Hostname, 9 and domain name, 9 HotJava, 393 Hotspots, 158 HP-UX, 439 HTML, 7, 9, 11, 46, 155 basics, 46–48 official standards, 38 operations, 120 viewing source code, 64 HTP/HTF Parameters, 171 HTTP, 7, 8, 10, 11, 76, 77, 102, 112 HyperCard, 7 Hyperlinks, 46, 130–32<br />
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Hypermedia, 8 future, 551–52 Hypertext, 6 Hypertext Markup Language. See HTML. Hypertext Transfer Protocol. See HTTP.<br />
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I IBM’s IMS database, 15 Image, 155 Image map, 67, 157, 174, 213, 223, 337, 402 creation, 190–92 management, 253 Implicit cursor, 542 Indexes. See also Concatenated index. concatenated, 488 and constraints, 493–94 guidelines, 486 multicolumn, 494 and Oracle performance, 496 tuning queries, 486–88 Inheritance, 21, 22, 395, 396 multiple, 21 Installation process, 72 Installer prompts, 78 Intel 486, 395 Interface definition vs. class definition, 400 Interfaces, 400 Internet, 1, 504 address, 3 applications, 2, 5 communication protocols, 2 components, 2 cost of connecting, 2 physical network, 2 vs. World Wide Web, 6 Internet Explorer, 71, 120 Internet Network Information Center. See InterNIC. Internet Protocol. See IP. Internet-based online systems, 12 future, 12 InterNIC, 4 Interscreen travel methods, 336 Intersystem connectivity, 436 Intranets, 8 Invoke, 375 IP, 3, 433, 442, 443 ISA relationship, 29, 548<br />
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J file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (7 of 18)4/03/2005 6:19:55<br />
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Java, 34, 41, 112, 118, 391–92, 542, 543 benefits of using, 42 creating dynamic HTML documents, 415 development, 392–93 error messages, 411 HTML examples, 416–19 object-orientation, 395–97 performance, 398 portability, 393–95 security, 397 vs. C++, 42, 395 vs. PL/SQL, 404 wrapper, 412 Java Cartridge, 33 Java Code fundamentals, 398–401 Java Interpreter, 41, 43, 401, 402, 404, 405 Java Virtual Machine, 393–94, 403 Java Web Toolkit, 43, 404, 405 JavaScript, 404 JDK, 411 Joint Photographic Experts Group. See JPEG. JPEG, 59, 60, 135, 337<br />
<br />
K Kimball, Dr. Ralph, 468 Korn shell, 153, 334, 372. See also CGI scripts.<br />
<br />
L Languages declarative, 526 object-oriented, 13, 23, 24, 25, 36, 45, 301, 302, 541 procedural, 291, 541 LAN, 11 LaTeX, 11 Link, 46, 376 references, 59 Linux, 394 List procedures, 168 Listener commands, 449 processes, 112, 452 LiveHTML, 34, 118, 419–29 cartridge, 33, 43 examples, 423–29 Interpreter, 401, 420 similarity to SGML, 421<br />
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syntax, 421–23 Local area networks. See LAN. Local mode, 382 Location transparency, 4, 432, 446 Lock chain, 385 Lock escalation, 384 Lock pool resources, 386 Locking, 489 solution, 379 Locks exclusive, 381 shared, 381 table-level, 385 Logging features, 145 Logical volume manager. See LVM. LVM, 520, 521<br />
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M MacOS, 394 Mailto protocol, 222 Managing Distributed Databases, 438 MAP files, formatting, 158 Massively parallel processors. See MPP. Master lookup table, 438 McCool, Rob, 152 Memory fencing. See Pinning. Message, 25 MetaCube, 547 Method, 396 coexistence, 381 Microsoft, 549 Access, 14 Internet Explorer, 11, 64 Visual Basic, 14 Windows, 6, 468, 551 and design issues, 124 MIME, 155, 278 types, 156 Mode conversational, 378, 382 pseudo-conversational, 378, 382 Model object-oriented, 16 Morphology, 547 Mosaic, 393 MPP, 500 MS Query, 373 MTS, 439, 440, 449, 450, 451 starting rules of thumb, 451 Multiprocessing, 497 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (9 of 18)4/03/2005 6:19:55<br />
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Multipurpose Internet Mail Extension. See MIME. Multitasking, 497 Multithreaded server. See MTS. Multithreading, 497<br />
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N Names facility, 446 National Center for Supercomputing Applications. See NCSA. National Language Support. See NLS. National Science Foundation, 2 Natural, 557 Natural language, 547 Navigation pathway complexity, 142 NCSA, 152 HTTPd, 36 Nelson, Ted, 6 Netscape, 11, 54, 64, 71, 94, 101, 120, 122, 124, 129, 135, 152, 251, 393 communications server, 36 and frames, 128 Network Computers and Java technology, 402 Network host, 11 Network Programmatic Interface. See NPI. NeXT, 7 NFSNET, 1 NIC, 4 NLS, 81, 89 Nobody, 86, 161 NPI, 441<br />
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O O2 technology, 549 Object administrator functions, 20 consolidator, 546 Data Management Group. See ODMG. Design, 549 identifier. See OID. Linking and Embedding. See OLE. Management Group. See OMG. privileges, 348 Request Broker. See ORB. technology, 12 Object-oriented approach, 547 database standard architecture, 549 databases, 545 languages. See Languages, object-oriented. paradigm, 22 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (10 of 18)4/03/2005 6:19:55<br />
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programming. See OOP. Objects aggregate, 19 and behaviors, associations, 17 ODMG, 18 ODMG Object Model, 548–51 OFA, 78 OID, 549 OLAP, 471 OLE, 551, 552 OMG, 18 Online English, 556 systems design, 138 video clips. See VID files. Ontos, 549 OODB, 548 OOP, 396 Open systems, 344 OPI, 441 OPS$, 446, 451 Optimal Flexible Architecture. See OFA. Optimizer cost-based, 458, 485, 491, 496, 521, 525, 537, 538, 539–40 rule-based, 458, 485, 496, 525, 526, 528, 535–39, 540 rule-based vs. cost-based, 539 Oracle7 database products, 72 Oracle8, 18, 19, 20, 27, 545–548 object layer, 18 Oracle bulletin #105025.433, 350 ConText, 546 database, 338 DBA, 297 Express, 547 and printing or downloading, 118 Programmatic Interface. See OPI. Sedona, 546 System ID. See SID. System Identifier, 73 table, 288 Web Administrative Server. See OWAS. Web Agent. See OWA. See also PL/SQL Agent. Web Agent DBA. See OWA_DBA. Web Listener. See OWL. Oracle Magazine’s home page, 64 Oracle RDBMS Database Administrator’s Guide, 537 Oracle WebServer, 133 3.0, log server, 148 installation, 76 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (11 of 18)4/03/2005 6:19:55<br />
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Installer, 74–76 uninstalling, 76, 85 Oraperl, 153, 154. See also CGI scripts. orasrv, 440. See also SQL*Net, listener process. ORB, 546 OS/2, 394, 497 Overloading, 24 OWA, 34, 77, 159, 338, 404 OWAS, 77, 100, 102 OWA_DBA, 95, 96, 97, 99, 104, 105 OWL, 33, 77, 85, 100, 155, 160, 403, 404, 504<br />
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P Package, 298, 349, 506, 508 wrapper, 406 Packets, 3 Pages framing, 174 levels, 142 Parallel query, 519–22 using, 500–502 Parallelism, 498, 499, 522. See also Client/server, parallelism. Partitioning, 180, 499, 520 Pattern, 268 Pellow, Nick, 7 People costs vs. CPU costs, 13 Perl, 112, 153, 154, 542, 543. See also CGI scripts. Persistence, 160 Personal Function,130, 131 Physical format procedures, 169 Pictures, 46 PID, 450 Pinging, 94, 100 Pinning, 507 automatic, 509 measuring packages, 509 PL/SQL, 41, 112, 134, 160, 291, 397, 412 problems, 299, 542 syntax structures, 292 tuning, 299–301, 541–44 PL/SQL Agent, 34, 36, 37, 159, 401, 403, 405, 504 Developer’s Toolkit, 107 packages, 408 procedure, 112, 114, 154 role, 38 stored procedure, 37 vs. Java Interpreter, 41 vs. Java Interpreter, 41 PL/SQL User’s Guide and Reference, 324 PL/SQL Web Toolkit file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (12 of 18)4/03/2005 6:19:55<br />
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and Java Web Toolkit, 404 Plain text, 155 Point-to-point lines, 2 Polymorphism, 23, 24, 25, 395, 547 Pop-up list, 63, 333 PowerBuilder, 118, 119, 126 Preemptive locks. See Locks, exclusive. Pre-spawned shadow. See Existing process. “Primacy of the user” principle, 145 Print procedures, 165 Prism, 497 Privileges combining, 350 object vs. system, 347 Pro*C, 450 Procedural Language/Structured Query Language. See PL/SQL. Procedures and packages problem, 349 Process ID. See PID. Processing improving speeds, 478 pseudo-conversational, 144 SMP vs. MPP, 500 Programming object-oriented, 15 profession, 15 Protocols, 2 application, 3 levels, 3 network, 3 transport, 3 Providing OLAP (Online Analytical Processing) to User-Analysts: An IT Mandate, 458 Public synonym, creating, 109<br />
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Q Query By Example, 557 See QBE.<br />
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R Radio buttons, 63, 333 RAID, 520, 521 Referential Integrity. See RI. Remote client, speed, 121 connection, 444 request, 444 Requests servicing, 112 Results file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (13 of 18)4/03/2005 6:19:55<br />
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non-reproducible, 382 RI, 482, 483, 486, 494 Roles, 345, 352, 355 creating, 361 Ronco, 23 Router, 11 Row information updating, 339–44 Rows phantom, 382 RTF, 11 Rule-based optimizer. See Optimizer, rule-based. Rules of normalization, 458, 474<br />
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S Sacks, Oliver, 554 Sanders, Tony, 152 Sargeable predicate, 486, 489 SAS, 14 Savvy, 557 Screen layout creation, 137 Screen transfer vs. hyperlinks, 130 Screen moving in WebServer, 376 transfer, 375 SDK, 125 Security, 344 achieving simplicity, 365 checks, 345 data-specific vs. application-specific, 361–63 in remote database, 355 starting guidelines, 373–74 stored procedure vs. role-based, 349 two methods for managing, 346 Selectivity, 485 Sequential pre-fetch, 487 Server Side Includes. See SSI. See also LiveHTML. ServerManager, 281 Service lines, 2 Service names, 443 SGA, 298, 506, 507, 509, 512 SGML, 11, 47, 420 Short On Storage. See SOS. SID, 407, 439, 442 Slow image display, problems, 120 SmallTalk, 15, 547. See also Languages, object-oriented. SMP, 500, 521 Snapshots, 474–82 complete refresh, 475 creating, 475 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (14 of 18)4/03/2005 6:19:55<br />
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fast refresh, 475 Software Asset Manager, 83–84, 91 Solaris, 394 space required, 74 Solaris Unix, 439 SOS, 381 Spawned, 450 SQL, 15, 20, 27 SQL cursors types, 299 SQL*DBA, 281 SQL*Forms, 118, 119, 121, 126, 130, 299, 312, 319, 327, 337, 341, 450, 483, 541 SQL*Net, 432, 436, 438–50, 478, 501, 505 1.0 vs. 2.0, 440 connection error message, 445 connections to remote databases, 443 connections types, 456 listener process, 447 ways to establish database communications, 444 SQL*Net Sessions viewing, 454–56 SQL*Plus, 27, 281, 354, 373, 445, 447, 454, 513 SSI, 43, 402, 420 Standard Generalized Markup Language. See SGML. Star schema design, 465–468 State, 396 Stored procedure, 297, 349, 356, 357, 377, 435, 441, 505, 508, 512 access, testing, 110 benefits, 505 Striping, 521 Structure procedures, 165 Structured Query Language. See SQL. Sun Microsystems, 392 SunSoft, 549 Symmetrical multiprocessing. See SMP. Synonyms, 353–54 System Global Area. See SGA. System privileges, 346, 347 Systems analysis purpose, 140 Systems design process purpose, 141<br />
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T Table, 129 HTML vs. Oracle, 243 partial replication, 481 privileges, 346 procedures, 170 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (15 of 18)4/03/2005 6:19:55<br />
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replication, 436, 474 Table-level security, 356 replacing, 360 Tags, 47 Target string, 256 Task-flow diagram, 141 TCL, 153, 154. See also CGI scripts. TCP, 3 TCP/IP, 3, 101, 439, 443 Technical support, 115 Telnet, 5 Temporary tables using, 534–35 Text, 46 alignment, 124 highlighting, 235 Thrashing, 506 TIFF, 60 Time zones, 255 Time-Warner, 393 TNS, 433, 435 TNS listener, 440 tnslsnr, 440. See also SQL*Net, listener process. Trace facility, 533 Tracking error messages, 146 Tranparent network substrate. See TNS. Transaction freezing, 144 global, 432 Transfer, 376 Transmission Control Protocol. See TCP. Triggers, 297, 350, 481, 505, 515 vs. stored procedures, 516 when to use, 516 2PC, 389, 453–54 Two-phase commit. See 2PC.<br />
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U UDP, 3 Uniform Resource Locator. See URL. Universal object manager, 546 Unix, 5, 424 documentation screen, 83 Updatable snapshots, 474 Update procedure, 303 UPI, 440, 441 URL, 8, 59, 85, 112, 280 components, 9 format, 9 User Datagram Protocol. See UDP. file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (16 of 18)4/03/2005 6:19:55<br />
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User Programmatic Interface. See UPI.<br />
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V Versant, 549 Vertical partition, 432, 436 VID files, 120 Video, 46, 155 Views, 357 Virtual reality environments. See VRML. Visual Basic, 153 Voice Recognition Database Access, 556–57 VRML, 120<br />
<br />
W WAIS, 3, 5 WAN, 1, 2 Web listener, 32, 33, 34, 35, 190 Web page constructs, 46 definition, 46 vs. SQL*Form or PowerBuilder, 126, 319 Web Request Broker. See WRB. Web technology, 8 Web Transaction Manager, 43–44 WebMaster, 161 WebServer, 29, 38–39, 312 3.0, 121 Administrative Server, default port, 92 applications, 118–19 basic components, 33 configuring WebServer 1, 94–100 configuring WebServer 2, 100–05 differences between versions 1 and 2, 34 installing WebServer 1, 76–85 installing WebServer 2, 85–93 primary purpose, 32 real benefit, 41 using, 71 West Publishing Company, 557 Whitney, Eli, 13 Wide-Area Information Servers. See WAIS. Wide-area network. See WAN. Widgets, 125, 126 Wildcards, extensions, 257 Windows, 394 Windows NT, 497 Windows Standard Development Kit. See SDK. Wizards, 15 World Wide Web, 6, 12 file:///F|/My%20Bookcase/Database/Oracle/Oracle%20Databases%20On%20The%20Web/book-index.html (17 of 18)4/03/2005 6:19:55<br />
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elements, 8 origin, 7 principles, 7 Wrappers, 405 WRB, 33, 34, 36, 85, 112, 151, 159, 160, 278, 378, 401, 402, 403, 404, 405, 420, 441, 448, 503, 504 executable engine. See WRBX. services, 86 vs. CGI, 35, 112, 161 WRBX, 36, 85 WWW, 5<br />
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Z Zone names, 9<br />
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In this example, the code includes a call to the image named myfile.gif. When the HTML document is viewed in a browser, the myfile.gif graphic will appear on the Web page where the image tag appears in the HTML document. In addition to the SRC parameter, the ALIGN parameter is a very useful extension within the IMG tag. The ALIGN tags normally indicate where a graphic will appear in relation to surrounding text. Here is the syntax used to align a graphic on a Web page