EXCI concepts

The external CICS® interface makes CICS applications more easily accessible from non-CICS environments.

Programs running in MVS™ can issue an EXEC CICS LINK PROGRAM command to call a CICS application programs running in a CICS region. Alternatively, the MVS programs can use the CALL interface when it is more appropriate to do so.

The provision of this programming interface means that, for example, MVS programs can:
  • Update resources with integrity while CICS is accessing them.
  • Take CICS resources offline, and back online, at the start and end of an MVS job. For example, you can:
    • Open and close CICS files.
    • Enable and disable transactions in CICS (and so eliminate the need for a main terminal operator during system backup and recovery procedures).

The external CICS interface opens up a new way to implement client/server applications, where the client program in a non-CICS environment calls a server program running in the CICS address space. The external CICS interface benefits not only TSO and batch applications, but allows you to extend the use of CICS application programs in an open client/server environment.

Although the CICS external interface operates over CICS MRO links, the client program can run on non-MVS platforms, and pass requests to CICS over an open system interface (OSI) using the IBM® z/OS® Distributed Computing Environment Application Support MVS/ESA CICS feature (DCE AS/CICS). In this way the external CICS interface provides an open interface to a wide variety of other application platforms.