The previous sections have introduced the three primary elements—ports, database links, and data sources—that comprise the Application Server program. If we combine these elements within the context of the Application Server’s role within the system, it becomes apparent how the client applications connect and communicate to the back end database engine. The Application Server defines a single ADSP or TCP/IP port and a Database Link that connects to the database through an ODBC Data Source.

Figure: Communication Process.

Client applications communicate through ports, database links, and ODBC data sources to connect to system databases residing on the back end database server.