Introducing FEPI functions

The CICS/ESA Front End Programming Interface (FEPI) function provides access, by means of simulated terminals, to CICS® and IMS™ applications available through a communication network. An application program using FEPI can provide a front end to other CICS or IMS applications. Because this is done by simulating a terminal in session with the non-FEPI application, that application does not have to be changed in any way.

Thus you can write FEPI applications that provide a single integrated interface to previously disparate applications. The scope and usability of your CICS and IMS applications can be extended by using them in combination, in different environments, or on different systems.

Because a FEPI application communicates with other applications that may run in different systems, it is necessary to distinguish between systems and identify the direction of data flows. The convention is:

Front-end
The front-end system is the one in which the FEPI application runs.
Back-end
Back-end identifies the system in which the other CICS or IMS applications run. (This is equivalent to "partner" system, used elsewhere by CICS.)
Outbound
Identifies data sent by the FEPI application to the back-end application.
Inbound
Identifies data received by the FEPI application from the back-end application.

FEPI provides a programming interface. Its functions can be invoked only through that interface, which is an extension to the EXEC CICS programming interface. All FEPI requests are made by issuing EXEC CICS FEPI commands; all the commands have the qualifier FEPI. The languages supported by the EXEC CICS programming interface (Assembler,COBOL, C, PL/I) can be used. For educational and initial development purposes, you could simply use CECI, rather than formally writing a program.

All functions are available in the normal way to all applications, except that some functions are intended for system programmers, and their use can be restricted. All the other facilities that you can use with CICS applications, such as the execution diagnostic facility (EDF) and the command interpreter transaction, CECI, are available.

Samples

To help you develop your own CICS FEPI applications, and to show you what FEPI can do, FEPI includes detailed samples. They form an integrated set, and include a program that sets up the FEPI configuration needed to run the other samples. The samples are supplied in source format. Their names have the form DFH0xZyy. Z shows that the sample is a FEPI sample and x identifies the source language of the sample (A for Assembler language, C for C, P for PL/I, and V forCOBOL), and yy identifies the specific program. See Appendix A. FEPI sample programs.

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