This topic describes the Oracle Applications Architecture and some of the features that this architecture supports. We will be learning about The Desktop Tier, The Application Tier, The Database Tier and The Oracle Applications Technology Layer.

Oracle Application Concepts - Internet Computing Architecture

The Oracle Applications Architecture, as shown in figure 1 below, is a framework for multi-tiered, distributed computing that supports Oracle Applications products. In this model, various servers are distributed among multiple levels, or tiers.

Desktop Tier Application Tier Database Tier
Figure 1. Oracle Applications Architecture

A server is a process or group of processes that runs on a single machine and provides a particular functionality, often referred to as a service. For example, the HTTP server is a process that listens for and processes HTTP requests, and the Forms server is a process that listens for and processes requests for activities related to Oracle Forms.

A tier is a logical grouping of services, potentially spread across more than one physical machine. The three-tier architecture that comprises an Oracle E-Business Suite installation is made up of the database tier, which supports and manages the Oracle database; the application tier, which supports and manages the various Applications components, and is sometimes known as the middle tier; and the desktop tier, which provides the user interface via an add-on component to a standard web browser.

The Desktop Tier

The client interface is provided through HTML for the newer HTML-based applications, and via a Java applet in a Web browser for the traditional Forms-based interface. In Oracle Applications Release 11i, each user logs in to Oracle Applications through the E-Business Suite Home Page on a desktop client web browser. The E-Business Suite Home Page provides a single point of access to HTML-based applications, Forms-based applications, and Business Intelligence applications.

a) Forms Client Applet

The Forms client applet is a general-purpose presentation applet that supports all

Oracle Applications forms-based products, including those with customizations and extensions. The Forms client applet is packaged as a collection of Java Archive (JAR) files. The JAR files contain all Java classes required to run the presentation layer of Oracle Applications forms.

b) Oracle JInitiator

The Forms client applet must run within a Java Virtual Machine (JVM) on the desktop client. The Oracle JInitiator component allows use of the Oracle JVM on web clients, instead of the browser’s own JVM. JInitiator is implemented as a plug-in (Netscape) or ActiveX component (Microsoft Internet Explorer). JInitiator is only invoked when a user chooses to access functions that require it, such as running a form. If JInitiator has not been installed, the Web browser prompts the user to download the required installation executable.

The Forms client applet and commonly used JAR files are downloaded from the Web server at the beginning of the client’s first session. Less commonly used JAR files are downloaded as needed. The JAR files are cached in a directory specified when JInitiator was installed.

The Application Tier

The application tier has a dual role: hosting the various servers that process the business logic, and managing communication between the desktop tier and the database tier. This tier is sometimes referred to as the middle tier. Oracle9i Application Server (9iAS) provides the technology used on the application tier. Six servers comprise the application tier for Oracle Applications:

a) Web server

The Oracle HTTP server (powered by Apache) acts as the Web server. It processes the requests received over the network from the desktop clients, and includes additional components such as:

- Web Listener

- Java Servlet Engine

- JavaServer Pages (JSP)

The Web listener component of the Oracle HTTP server accepts incoming HTTP requests (for particular URLs) from client browsers.

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