Release 3.3.57.25
A86662-01
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| Oracle Discoverer Oracle Discoverer 3i Viewer Configuration Guide for Oracle Internet Application Server for Unix Release 3.3.57.25 A86662-01 |
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Oracle Discoverer 3i Viewer is a business intelligence tool for viewing workbooks created by users of the client/server or web releases of Discoverer Plus (previously known as Discoverer User Edition). Using Oracle Discoverer's easy to use interface via a web browser, users can access and analyze database data.
Oracle Discoverer 3i Viewer is straightforward to set up and maintain. Oracle Discoverer 3i Viewer can be used to integrate database output into your web site and portal and is easily customized to fit in with your web site look and feel, or to build custom Discoverer applications for the web. Oracle Discoverer 3i Viewer is also optimized for performance and designed to minimize network traffic.
This chapter provides an overview of the Oracle Discoverer 3i Viewer architecture, describes the components and illustrates how Oracle Discoverer 3i Viewer works to give data access to users.
Oracle Discoverer 3i Viewer is installed as part of Oracle Internet Application Server (iAS). The default installation is a single machine installation (i.e. all the Discoverer components are installed on a single machine).
Oracle Discoverer 3i Viewer can be used to view workbooks created by Discoverer Plus on client/server or the web. The deployment of Oracle Discoverer 3i Viewer is best understood by looking at its context (see Figure 1-1).
Oracle Discoverer 3i Viewer is deployed using an Internet computing architecture that sits on top of the existing Discoverer Services.
Oracle Discoverer Services works with the Oracle iAS HTTP listener to provide a robust, scalable deployment platform for the Oracle Discoverer 3i Viewer.
The n-tiers of Discoverer are as follows:
This architecture takes advantage of the distributed nature of the web environment.
The first tier is the client--a user's computer. There is no setup or installation to do on the client machine, nor does this machine need to have access to any database. The only requirement for this computer is that it can run HTML through a web browser, such as Microsoft Internet Explorer 4.01 or Netscape Navigator 4.0. By accessing the URL that you (the Discoverer administrator) provide, users can connect and run Oracle Discoverer 3i Viewer to view data.
The second tier is the HTTP Server having the Discoverer 3i Viewer Servlet installed in the HTTP Server's Servlet engine. The Locator must be accessible from the HTTP server.
A Servlet comprises modules of Java code that run as a server application to answer HTTP requests (hence the name "Servlets", similar to "Applets" which are used on the client side). The Servlet minimizes any client-side processing.
A Servlet Engine comes as part of (or a plug in to) an HTTP Server and is the environment in which the Servlet runs. The Servlet Engine incorporates a Java Virtual Machine (JVM) and implements the Java Servlet API.
The HTTP server (Servlet engine) contains the following components:
The Discoverer Servlet generates HTML pages from HTTP requests using an XSL processor.
The third tier is the Discoverer Services. The Server consists of three basic components: the Locator, the Session, and the Preferences.
The components are installed on one or more application servers. You can install Discoverer Services on one machine or across many machines. For more information on install Discoverer Services across multiple machines see the release notes.
In addition, two CORBA (Common Object Request Broker Architecture) components from VisiBroker--an Object Activation Daemon (OAD) and a SmartAgent component--are also installed. These CORBA components are responsible for activating new components and providing a location service whenever the user requests to begin a Discoverer session.
The Discoverer Services contains the following components:
A Discoverer server session is created for each user and performs all the business intelligence of Discoverer 3i Viewer for a given user. Once a session is started, it is the user's instance of Discoverer 3i Viewer. The Session component contains all of the application logic and performs all of the Discoverer operations such as connecting to the database or opening a workbook.
Machines with a Session component installed can run multiple concurrent sessions for clients.
The purpose of the Locator is to receive a request for a session from the Servlet (the request is initiated after a URL is sent to the Servlet from the client browser), find the next application server, start a new session, and return a reference for the new session back to the Servlet. Once the Servlet has received this reference, the Servlet and the session communicate with each other and the Locator waits for the next request. The Locator component is installed on the HTTP server. You need only one Locator component on the network for the Discoverer Services.
You should only have one Preferences component for a Discoverer Services environment. So if you have five machines running Discoverer Services, the Preferences component should only be running on one of them. Preference settings are used by Discoverer Services to dictate certain aspects of behavior.
The fourth tier of Discoverer is the database. The database contains the data users want, the End User Layer (EUL) that provides an easy to understand view of the data, and the Discoverer workbooks that users can work with to view and analyze the data. The EUL is created and maintained with the Discoverer Administration Edition.
This section describes how Oracle Discoverer 3i Viewer works--from the point when the user launches the browser on the client computer to when data access becomes available. The following figure illustrates the basic process.
Oracle Discoverer 3i Viewer is invoked via a URL from a standard web Browser.
The URL is processed by a Servlet running in the Servlet engine. The Servlet uses the Locator to communicate with the Discoverer Services.
The Oracle Discoverer 3i Viewer Servlet interprets the HTTP request from the client browser, and makes the necessary calls to the Discoverer Services.
The server response represented in XML is generated by the Servlet and sent to an XML/XSL processor.
XML/XSL processor combines XML with an XSL configuration file that defines the representation of the User Interface and generates the output (e.g. HTML) to send back to the browser.
The Oracle Discoverer 3i Viewer is composed of two primary layers - the application logic and the presentation logic.
The application logic manages the handling of the HTTP request, the state of the Discoverer Services, and generates the XML representing the logical state of the Discoverer server and the data for a given client.
The presentation logic takes the XML and uses XSL to generate a response in a given format (e.g. HTML, MicroSoft Excel, XML etc.). The presentation logic can be customized to alter the appearance of user interface (by editing XSL files). See Chapter 4, "Customizing Oracle Discoverer 3i Viewer" for details.
The Oracle Discoverer 3i Viewer Servlet and Discoverer Services are automatically installed to run on the Oracle Internet Application Server as a single machine installation. However they are designed to be deployed on multiple machines (See the release notes for further information). The Discoverer Services can be replicated by specifying the machines available to Discoverer in a configuration file. Discoverer Services sessions are then started on alternate machines to balance the load.
In this way very large numbers of Discoverer Users may be supported, since there is no single bottleneck. Multiple Discoverer sessions can run on a single machine, or can be spread across multiple machines as required.
The Discoverer 3i Viewer servlet can also be distributed.
In Figure 1-5 two HTTP servers are used to spread the load for three browser sessions. There are three server machines, with Discoverer Services running on each. In a real system there would be many users using each HTTP and application server. Discoverer allows you to determine exactly how you want to spread the load across the available machines.
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