Message and program-to-program switches

Message switches are queued globally in a shared queue environment. Program-to-program switches are eligible to be considered for local-first optimization. If the program-to-program switch message is not selected for local-first processing, then it is queued globally.

If the destination of a message switch is not defined on the local IMS, the Destination Creation exit routine (DFSINSX0) is called to identify the destination.

While ETO is active, if the exit routine indicates that the destination is an LTERM, the exit routine creates a dynamic user structure for the LTERM and then queues the message.

The DFSINSX0 exit can also indicate that the destination is a transaction. IMS will create the transaction based on the environment and options provided by the exit:

In a shared-queues environment without DRD, IMS will create a queuing-only transaction and queue the message globally.
In a shared-queues environment with DRD enabled, IMS will create a transaction either for queueing or for scheduling, as requested by the exit.