CICS FEPI application programs

A CICS® FEPI application comprises several distinct logical functions:

Access programs:
Communicate with the back-end applications
Begin-session handler:
Handles begin-session processing
End-session handler:
Handles end-session processing
STSN handler:
Assists message synchronization
Unsolicited-data handler:
Handles unsolicited inbound data
Monitor:
Handles unexpected events such as the loss of a session or errors in setup.

These functions can be in separate programs, or contained in one program. The need for each function depends on the requirements of the application; in many cases default processing is all that you need. You might need several styles of each function, again depending on the requirements of your application.

The application programmer always writes the access programs. The system programmer usually writes the monitors to handle the unexpected events that FEPI reports to transient data queues such as CSZX. As for the other functions, sometimes the system programmer writes them providing, perhaps, just one instance of each, so that they are common to everyone. (This approach has the advantage that adherence to standard procedures--for such things as signon and signoff--is enforced.) In other installations, the application programmers provide them.

In many cases, writing a CICS FEPI application is straightforward. However, some applications need more sophisticated programming. The programmer not only has to understand all the displays and protocols of the back-end application and system (CICS or IMS™), but must also understand the detailed data-stream protocols. For further information, see FEPI application design.

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