In this book, monitoring is specifically used to describe regular checking of the performance of a CICS® production system, against objectives, by the collection and interpretation of data. Subsequently, analysis describes the techniques used to investigate the reasons for performance deterioration. Tuning may be used for any actions that result from this analysis.
Monitoring should be ongoing because it:
A performance history database (see Tivoli Decision Support for z/OS for an example) is a valuable source from which to answer questions on system performance, and to plan further tuning.
Monitoring may be described in terms of strategies, procedures, and tasks.
Strategies may include:
Procedures, such as good documentation practices, should provide a management link between monitoring strategies and tasks. The following should be noted:
Tasks (not to be confused with the task component of a CICS transaction) include:
You should allocate responsibility for these tasks between operations personnel, programming personnel, and analysts. You must identify the resources that are to be regarded as critical, and set up a procedure to highlight any trends in the use of these resources.
Because the tools require resources, they may disturb the performance of a production system.
Give emphasis to peak periods of activity, for both the new application and the system as a whole. It may be necessary to run the tools more frequently at first to confirm that the expected peaks correspond with the actual ones.
It is not normally practical to keep all the detailed output. Arrange for summarized reports to be filed with the corresponding CICS statistics, and for the output from the tools to be held for an agreed period, with customary safeguards for its protection.
Conclusions on performance should not be based on one or two snapshots of system performance, but rather on data collected at different times over a prolonged period. Emphasis should be placed on peak loading. Because different tools use different measurement criteria, early measurements may give apparently discrepant results.
Your monitoring procedures should be planned ahead of time. These procedures should explain the tools to be used, the analysis techniques to be used, the operational extent of those activities, and how often they are to be performed.