Assessing the performance of your system

You may find the following performance measurements helpful in determining the performance of a system:

  1. Processor usage: This item reflects how active the processor is. Although the central processor is of primary concern, 37X5 communications controllers and terminal control units (these can include an intelligent cluster controller such as the 3601 and also the 3270 cluster control units) can also increase response time if they are heavily used.
  2. I/O rates: These rates measure the amount of access to a disk device or data set over a given period of time. Again, acceptable rates vary depending on the speed of the hardware and response time requirements.
  3. Terminal message or data set record block sizes: These factors, when combined with I/O rates, provide information on the current load on the network or DASD subsystem.
  4. Indications of internal virtual storage limits: These vary by software component, including storage or buffer expansion counts, system messages, and program abends because of system stalls. In CICS®, program fetches on nonresident programs and system short-on-storage or stress messages reflect this condition.
  5. Paging rates: CICS can be sensitive to a real storage shortage, and paging rates reflect this shortage. Acceptable paging to DASD rates vary with the speed of the DASD and response time criteria. Paging rates to expanded storage are only as important as its effect on processor usage.
  6. Error rates: Errors can occur at any point in an online system. If the errors are recoverable, they can go unnoticed, but they put an additional load on the resource on which they are occurring.

You should investigate both system conditions and application conditions.

System conditions

A knowledge of these conditions enables you evaluate the performance of the system as a whole:

Application conditions

These conditions, measured both for individual transaction types and for the total system, give you an estimate of the behavior of individual application programs.

You should gather data for each main transaction and average values for the total system. This data includes:

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