Limiting concurrent requests for resources

To prevent any one job, started task, or TSO/E user from generating too many concurrent requests for resources, the control program counts and limits the number of ENQ requests in each address space. When a user issues an ENQ request, the control program increases the count of outstanding requests for that address space by one and decreases the count by one when the user issues a DEQ request.

ENQ RET=TEST, RET=CHNG, and ISGENQ equivalents do not cause this count to increase because they do not queue up a new request block. A GQSCAN resulting in a continuation TOKEN however, along with the ISGQUERY equivalent, does cause to count to increase.

Prior to an abend, messages ISG368E and ISG369I monitor address spaces that are approaching the request maximum. If a particular subsystem requires more ENQs than normal, use the ISGADMIN service to raise that subsystem's maximum for unauthorized and authorized requesters. As a temporary workaround, you can raise the overall system maximum by issuing the following commands:
When the computed count reaches the threshold value or limit, the control program processes subsequent requests as follows:
Parent topic: Serializing access to resources (ISGENQ macro)