With z/OS V1R3, enqueue management has been improved with a more sophisticated enqueue promotion algorithm.

An address space or enclave is promoted in terms of dispatch priority when it holds a resource that another higher priority address space or enclave wants to have. The resource manager indicates this situation to SRM through an ENQHOLD sysevent. By promoting the address space or enclave for a limited amount of time, the system hopes that the holder gives up the resource faster than it usually would with a lower DP. Also, while being promoted, the system ensures that the address space or address space associated with the enclave is not swapped out.

When a contention disappears, the resource manager notifies SRM through an ENQRLSE sysevent.

The enqueue promotion interval can be set by the installation through the ERV option in IEAOPTxx parmlib member. The ERV option specifies the CPU service units, that an address space or enclave can absorb while it is promoted before the promotion is taken back.

In goal mode, the enqueue promotion dispatch priority is determined dynamically at every policy adjustment interval (10 sec). It can change based on available processing capacity and amount of high dispatch work in the system. Address spaces are promoted to that priority, if their current dispatch priority is not already higher than that.

Before z/OS V1R3, an address space or enclave was only promoted once for a given resource. If the resource wasn't returned before the expiration of the promotion interval, it was just a nice try.

With z/OS V1R3, an address space or enclave is re-promoted by SRM for every contention indication from the resource manager. Also, while there is an outstanding contention release notification, quiesced work is kept swapped-in as long as there is ready work to run. This includes address spaces associated with enclaves.