Dependent region connections

At dependent region termination, the Signoff and Terminate Identify exit routines are not activated unless the control region connection is to be terminated.

That is, the dependent region Signoff and Terminate Identify exit routines are activated only when the IMS system continues to run without a connection to the external subsystem, such as when either the external subsystem has posted the termination ECB provided on the identify, the ESAP has activated the IMS Subsystem Termination Service, or IMS has processed a /STOP SUBSYS command. Otherwise, IMS does not communicate dependent region termination to the external subsystem.

IMS expects the external subsystem to monitor the dependent TCB with a z/OS® End Of Task (EOT) exit routine. The subsystem should do any signoff and terminate identify processing it requires when the EOT exit routine is notified of the region termination.

The external subsystem must also monitor EOT exit routine for dependent regions for which a thread was created. When an application program terminates abnormally, the Terminate Thread exit routine is not called.

When the control region connection is to be broken, a signoff followed by a terminate identify is done for the dependent region at region termination or after thread termination if a thread was active when the request to break the system connection was received. The Signoff exit routine is called only once even though more than one signon might have been done for the region. IMS continues its signoff and terminate identify processing and does not reactivate these exit routines if they encounter errors.