This section gives you information about what to do if you are aware that a task is in a wait state, or if CICS® has stalled during:
It contains the following topics:
If CICS has stalled, turn directly to What to do if CICS has stalled.
If you have one or more tasks in a wait state, you should have already carried out preliminary checks to make sure that the problem is best classified as a wait, rather than as a loop or as poor performance. If you have not, you can find guidance about how to do this in Classifying the problem.
You are unlikely to have direct evidence that a CICS system task is in a wait state, except from a detailed examination of trace. You are more likely to have noticed that one of your user tasks, or possibly a CICS user task--that is, an instance of a CICS-supplied transaction--is waiting. In such a case, it is possible that a waiting CICS system task could be the cause of the user task having to wait.
For the purpose of this section a task is considered to be in a wait state if it has been suspended after first starting to run. The task is not in a wait state if it has been attached to the transaction manager but has not yet started to run, or if it has been resumed after waiting but cannot, for some reason, start running. These are best regarded as performance problems. Tasks that are ready to run but cannot be dispatched might, for example, have too low a priority, or the CICS system might be at the MXT limit, or the CICS system might be under stress (short on storage). If you think you might have such a problem, read Dealing with performance problems.
Most tasks are suspended at least once during their execution, for example while they wait for file I/O to take place. This is part of the regular flow of control, and it gives other tasks a chance to run in the meantime. It is only when they stay suspended longer than they should that a problem arises.
There are two stages in resolving most wait problems involving user tasks. The first stage involves finding out what resource the suspended task is waiting for, and the second stage involves finding out why that resource is not available. This section focuses principally on the first of these objectives. However, in some cases there are suggestions of ways in which the constraints on resource availability can be relieved.
If you know that a CICS system task is in a wait state, it does not necessarily indicate an error in CICS. Some system tasks spend long periods in wait states, while they are waiting for work to do. For more information about waiting system tasks, see CICS system task waits.