mod_oc4j
负载均衡的角色，用于连接Oracle HTTP Server与OC4J的实例，mod_oc4j会从众多OC4J的实例中根据负载情况选取一个来传递请求。
When running Oracle Application Server,
the module mod_oc4j is the connector from Oracle HTTP Server to one or more OC4J instances.
Each OC4J process within an OC4J instance runs in its own Java Virtual Machine (JVM) and is responsible for parsing J2EE requests and generating a response. When a request comes into Oracle HTTP Server, mod_oc4j picks an OC4J process and routes the request to the selected OC4J process. Within each OC4J instance all of the OC4J JVM processes use the same configuration and start with the same Java options. Likewise, unless a process dies or there is some other problem, each OC4J process that is part of an OC4J instance has the same J2EE applications deployed to it.
mod_plsql
Mod_PLSQL interface for executing PL/SQL stored procedures in an Oracle database。mod_plsql provides support for building PL/SQL-based applications on the Web. PL/SQL stored procedures retrieve data from a database and generate HTTP responses containing data and code to display in a Web browser.
The Oracle HTTP Server receives a PL/SQL Server Page request from a client browser.
The Oracle HTTP Server routes the request to mod_plsql.
The request is forwarded by mod_plsql to the Oracle Database. By using the configuration information stored in your DAD, mod_plsql connects to the database.
mod_plsql prepares the call parameters, and invokes the PL/SQL procedure in the application.
The PL/SQL procedure generates an HTML page using data and the PL/SQL Web Toolkit accessed from the database.
The response is returned to mod_plsql.
The Oracle HTTP Server sends the response to the client browser.
The procedure that mod_plsql invokes returns the HTTP response to the client. To simplify this task, mod_plsql includes the PL/SQL Web Toolkit, which contains a set of packages called the owa packages. Use these packages in your stored procedure to get information about the request, construct HTML tags, and return header information to the client. Install the toolkit in a common schema so that all users can access it.
mod_osso
Oracle EBS R12单点登录（SSO）解决方案的代理。见： http://blog.csdn.net/pan_tian/article/details/8691726
