The IXLYCEPL macro provides the format of the contention exit parameter list. Include that macro as well as IXLYCON in your program.

When the contention exit returns to XES, you can no longer access the data in the CEPL.

The contention exit cannot consider that a request that it has granted is processed to completion until the system informs you of the result of your request. In general, the contention exit should neither make any assumptions about the success of its grants of resource requests nor keep a local image of the resource request queue.

You should be aware that if the contention exit indicates that the notify exits of resource owners are to be executed, the contention exit will not be invoked again until XES has been able to execute the specified notify exits and apply the results to the resource request queue. This dependency introduces the possibility of a user's protocol creating a deadlock condition. For example, issuing a synchronous IXLLOCK request to release a resource from within a notify exit that is executing on behalf of the same resource is one such case in which a deadlock could occur. (The contention exit will not be able to receive control again to process the request until the current set of notify exits (which are suspended awaiting completion of the request) are able to complete.)

XES does not support the detection or resolution of deadlock scenarios. The prevention of such occurrences is the responsibility of the connected users of XES services.