The following operational techniques can be used to influence the performance and efficiency of the CICS® system:
The CICS system initialization parameter MXT specifies the maximum number of user tasks that can exist in a CICS system at the same time. MXT is invaluable for avoiding short-on-storage (SOS) conditions and for controlling contention for resources in CICS systems. It works by delaying the creation of user tasks to process input messages, if there are already too many activities in the CICS system. In particular, the virtual storage occupied by a message awaiting processing is usually much less than that needed for the task to process it, so you save virtual storage by delaying the processing of the message until you can do so quickly.
Transaction classes are useful in limiting the number of tasks of a particular user-defined type, or class, if these are heavy resource users.
CICS only resets a task’s runaway time (ICVR) when a task is suspended. An EXEC CICS command cannot be guaranteed to cause a task to suspend during processing because of the unique nature of each CICS implementation. The runaway time may be exceeded causing a task to abend AICA. This abend can be prevented by coding an EXEC CICS SUSPEND command in the application This causes the dispatcher to suspend the task that issued the request and allow any task of higher priority to run. If there is no task ready to run, the program that issued the suspend is resumed. For further information about abend AICA, see the CICS Problem Determination Guide.
Use auxiliary trace to review your application programs. For example, it can show up any obviously unnecessary code, such as a data set browse from the beginning of a data set instead of after a SETL, too many or too large GETMAIN commands, failure to release storage when it is no longer needed, unintentional logic loops, and failure to unlock records held for exclusive control that are no longer needed.