Using the XPCERES exit to check the availability of resources on the target region

You can use an XPCERES global user exit program to check that all resources required by the 3270 user transaction are available on the target region.

The exit is invoked, if enabled, on the target region before CICS® processes a dynamically-routed Link3270 bridge request.

If, for example, the 3270 user transaction is disabled on the target region, or a required file is missing, your exit program can give the dynamic routing program the opportunity to route the request to a different region. To do this, it should set a return code of UERCRESU. This causes CICS to:
  1. Return a RESUNAVAIL condition on the EXEC CICS LINK call to DFHL3270 executed by the mirror on the target region
  2. Set the DYRERROR field of the routing program's communications area to 'F'—resource unavailable
  3. Reinvoke the routing program, on the routing region, for route selection failure—see Handling route selection errors of Link3270 bridge requests

For information about writing an XPCERES global user exit program, see Program control exits XPCREQ, XPCERES, XPCREQC.

If a required resource is unavailable on the target region, but the XPCERES exit is unavailable or disabled (or is enabled but does not set the UERCRESU return code), the client program receives an error response.