Considerations on Attention Interruptions with IKJEFTSR

If you choose isolated environment TSO/E also isolates the active attention exits. If you choose unisolated environment this is not the case and you may find that the wrong attention exit gets control.

The application program issuing the TSO/E Service Facility routines may as well use the STAX macro to process attention interruptions. The STAX macro is to specify the address of an attention exit routine in your application program that gains control when an attention interruption occurs.

On the other hand, the commands, programs, CLISTs, or REXX execs invoked with the TSO/E Service Facility routine IKJEFTSR may have their own attention interruption processing.

If your application program issues its own STAX macro it may be required to temporarily relinquish its control if you want the invoked function's attention interruption processing to take control. Consider the following sequence, which shows how an application relinquishes control of its attention exit while the TSO/E Service Facility is executing:

The application indicates that its attention exit is to receive control:
STAX exit_address, USADDR= …

During application processing, its attention exit will receive control if an attention interruption occurs.
The application relinquishes control of its attention exit before invoking IKJEFTSR:
STAX
The application invokes IKJEFTSR.
After IKJEFTSR has finished the application reestablishes its own attention processing:
STAX exit_address, USADDR= …

If the TSO/E Service Facility is invoked and an ISPF service is invoked from within, it is required to temporarily relinquish control; else ISPF will not be able to perform its attention processing.

For further details see Using the STAX service routine to handle attention interrupts and z/OS TSO/E Programming Guide about processing attention interruptions.