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MVS Waits

Introduction

CPU Wait (CTL)

CPU Wait (DEP)

Swapping In

CTL Private Page

MVS Waits

The process of executing a thread or a batch message processing region can be blocked by contention for resources managed by MVS (rather than by IMS), such as the CPU. The individual execution states in this group show you when and where threads get slowed down by resources managed by MVS.

The collector found the thread ready to run on a CPU within the IMS control region, but all online CPUs in the complex were running other work. The CPUs might be running other IMS control region tasks, IMS dependent regions, or memories not related to IMS, such as TSO.

Note: The collector does not count itself in this analysis. If the only reason a thread is not executing on a CPU is that the collector is executing, the collector counts the thread as Using CPU. This is a standard sampling technique for measuring CPU usage by workload.

Also, the collector cannot see CPU Waits resulting from work executing with a higher dispatching priority than the collector. For example, the collector cannot see CPU Waits resulting from disabled global SRB, higher priority address spaces such as *MASTER*, and local SRBs in the IMS CTL region. If there is much of this higher priority activity, it will skew the measurements. Some amount of CPU Waitand perhaps even other states such as Database I/O Waitare seen as Using CPU.

The collector found the thread ready to run on a CPU within its region, but all online CPUs in the complex were running some other MVS address space. The CPUs might be running the IMS control region, other dependent regions, or address spaces not related to IMS, such as TSO.

The collector found the thread active inside a CICS&tm. region which was in the process of being swapped in by MVS.

The collector found the thread waiting for one of the following reasons:

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.

Bottleneck Analysis Execution States

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