Methods of performance analysis

You can use two methods for performance analysis:

  1. Measuring a system under full production load (full-load measurement), to get all information that is measurable only under high system-loading.
  2. Measuring single-application transactions (single-transaction measurement), during which the system should not carry out any other activities. This gives an insight into the behavior of single transactions under optimum system conditions.

Because a system can have a variety of problems, we cannot recommend which option you should use to investigate the behavior of a system. When in doubt about the extent of a problem, you should always use both methods.

Rapid performance degradation often occurs after a threshold is exceeded and the system approaches its ultimate load. You can see various indications only when the system is fully loaded (for example, paging, short-on-storage condition in CICS®, and so on), and you should usually plan for a full-load measurement.

Bear in mind that the performance constraints might possibly vary at different times of the day. You might want to run a particular option that puts a particular pressure on the system only at a certain time in the afternoon.

If a full-load measurement reveals no serious problems, or if a system is not reaching its expected performance capability under normal operating conditions, you can then use single-transaction measurement to reveal how individual system transactions behave and to identify the areas for possible improvement.

Often, because you have no reliable information at the beginning of an investigation into the probable causes of performance problems, you have to examine and analyze the whole system.

Before carrying out this analysis, you must have a clear picture of the functions and the interactions of the following components:

In addition, you should collect the following information:

Related tasks
CICS performance analysis techniques
What to investigate when analyzing performance
Information sources to help analyze performance
Establishing a measurement and evaluation plan
Assessing the performance of your system
Performance analysis: full-load measurement
Performance analysis: single-transaction measurement
Identifying CICS constraints
Tuning your CICS system
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