Notify Exit Routine Processing

Within the notify exit, you can modify the NEPL to indicate the action to be taken. To commit the changes to the NEPL, you must call the IXLSYNCH service from the notify exit. The IXLSYNCH service provides a synchronous update of the state and/or user data associated with a resource. If you modify the NEPL and do not call the IXLSYNCH service, any changes made in the NEPL are ignored. When all notify exits are complete, the contention exit is given control with a CEPL reflecting all changes made in the notify exits.

Changes that the notify exit might make in the NEPL are:

Update state and/or user data
The notify exit can update the state data through the NEPLOSTATE field and then issuing the IXLSYNCH macro. Similarly, the user data can be updated through the NEPLOUDATA field. Updates to these areas will be reflected in the CEPL fields CEPLEHSTATE and CEPLEHUDATA passed to the contention exit.
Release ownership of the resource
The notify exit can release ownership of the resource by setting the NEPLOSTATE field to the value (in IXLYCON) meaning “free” (IXLSTATEFREE) and then issuing the IXLSYNCH macro. When the contention exit receives the updated information in the CEPL, both CEPLEHSTATE and CEPLERSTATE will be set to “free”. This avoids the confusion that might arise with a request to obtain a resource, where CEPLEHSTATE is set to “free” and CEPLERSTATE is shared or exclusive.

When a user relinquishes interest in a resource within the notify exit, any outstanding requests from the user to alter or release the resource will fail with an indication that the specified resource is not found.

Upon completion of each invoked notify exit, XES gathers the ownership information that corresponds to the resource that caused the notify exit to be given control and applies the changes to the resource request queue. When the results of all invoked notify exits are available, XES invokes the managing contention exit and passes to it the modified resource request queue.

Note that a connector can be notified multiple times by the contention exit that is managing the resource contention. This will occur whenever the contention exit requests that notify exits again be given control after the results of the previous set of notify exits are presented to the contention exit. This ability to communicate allows multiple users to negotiate for lock ownership.