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MVS Waits

Cross Memory Page

The collector found the thread active inside a CCTL. The IMS system was running with LSO=X. The application program processing the thread had issued a DL/I call which was being processed by IMS modules running in the control region, but under the ASCB/TCB of the thread through the MVS Cross Memory Services. DL/I processing had taken a page fault for a page in the control regions private area.

In this situation, the threads execution is suspended while the page fault is resolved. Processing by the IMS control task is unaffected.

CTL Private Page (GFA)

The collector found the thread active. The application program processing the thread was ISWITCHed to the IMS control region, and one of two things happened:

Its ITASK took a page fault for a page in the private area of the control regions address space.

Its ITASK was ready to use the CPU, but it was waiting in the IMS dispatchers READY queue while the control task was serialized by a page fault taken in the private area by some other ITASK.

In either case, the page fault occurred at a time when the Available Frame Queue (AFQ) was empty, so the request for the resolution of the page fault had to be put on a special Real Storage Manager (RSM) queue, called the General Frame Allocation (GFA) queue, while the System Resources Manager (SRM) stole frames to replenish the AFQ.

GFA wait is not a major problem, because SRM STEAL is not the only source of replenishment for the AFQ. Every time an address space is physically swapped out, the frames it occupied go on the AFQ. Also, when a FREEMAIN is issued, all frames backing the virtual storage released are made available.

DEP Private Page (GFA)

The collector found the thread active. The application program processing the thread (or possibly some IMS module running as a subroutine of the application program) was waiting for the resolution of a page fault for a page in its private area. The request for resolution of the page fault was found on the general frame allocation (GFA) queue, indicating that it had occurred when RSM was out of frames (AFQ of 0).

Refer to the discussion of GFA under See CTL Private Page (GFA)on page 205.

Bottleneck Analysis Execution States

205

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