CICS monitoring facility: Performance and tuning

The CICS® monitoring facility collects data about the performance of all user-supplied and CICS-supplied transactions during online processing for later offline analysis. Monitoring data is useful for performance, tuning, and for charging your users for the resources they use. The records produced by CICS monitoring are of the MVS™ System Management type 110 and they are written to an SMF data set.

Collecting and processing data for CICS monitoring has information about the different types of monitoring data.

In terms of performance, collecting performance class data can be a significant overhead. The overhead is likely to be about 5% to 10%, but depends on the workload. MVS address space or RMF data can be gathered whether or not the CICS monitoring facility is active, to give an indication of the performance overhead incurred when using the CICS monitoring facility. CICS Monitoring Domain statistics show the number of monitoring records produced of each type.

If you do not need accounting information because other billing processes exist, and you have other means of gathering any performance data required, do not use the CICS monitoring facility to collect performance class data. Do not collect exception class data if you do not require it.

Recording of monitoring data incurs an overhead, but, to tune a system, both performance and exception information might be required. If tuning is not a daily process, the CICS monitoring facility might not need to be run all the time. When tuning, run the CICS monitoring facility during peak volume times because at those times performance problems typically occur.

To help reduce the overhead, data compression for monitoring records is set as the default. If overuse of the SMF data set is a potential problem, consider excluding fields from monitoring records.

Controlling CICS monitoring explains how to set CICS monitoring facility options using system initialization parameters and how to change these options while CICS is running.