Appls Architecture
R12 there are 3 tiers
Desktop Tier
Application Tier
Database Tier
Deskptop Tier: Its a web browser frrom which end-user logs into the application. The browser has to be java enabled. The desktop tier contains Forms Client Applet and Oracle Jinitiator.
* Forms Client Applet
Most of the Oracle Applications is based on Oracle Forms and Reports (Oracle Developer) and to display oracle forms on a client’s browser an applet is used. This forms client applet displays Oracle Applications screens and support field level validation, multiple windows and list of values (LOVs). The forms client applet is paclaged as Java Archive (JAR) files that contain all java classes for forms applet. These jar files are downoaded from Web server at the beginning of the client’s session and remains in the cache known as Jcache.* Oracle Jinitiator
The Forms Client Applet must run within a Java Virtual Machine (JVM) on the client machine. For Oracle Apps the JVM is provided by Oracle Jinitiator which acts as a plug-in (Active X componant in IE) in the web browser. When end-user enters the desired Oracle Applications signon URL withing the web browser, the browser will execute the Oracle Jinitiator.
Application Tier : The application Tier,is the location of application servers. This Tier is sometimes referred to as middle tier and provided business logic and code processing. There are five servers in Applications tier
HTTP server
Forms server
Concurrent Processing Server
Reports Server
Admin Server
Database Tier : The database tier contains the Data Server and holds all the data stored and maintained by Oracle Applications system. There are basically two types of database objests: Data Objects like Oracle apps Tables, Indexes, sequences etc.. and Code Objects like Stored Procedures, Packages, functions,triggers etc. Database Tier does not communicate with the desktop tier directly, Application tier provides the end user with information.