CICS statistic records are a rich source of performance information. They differ from CICS Management Facility
(CMF) performance records in that they do not track individual transaction activity. Instead, statistic records measure the use of CICS and system resources. Best of all, proper recording, archiving and reporting allows you to keep track of your overall performance and even discover some bottlenecks before they become serious problems.
CICS writes statistics records as SMF type 110's along with the CMF performance and exception data. IBM states that CICS gathers the statistics at a relatively low overhead cost. However, you cannot select which statistics you want to record, you may only turn them on or off. You can, however, control how often the records are written with the STATINT system initialization table (SIT) parameter or with the "EXEC CICS SET STATISTICS" command.
There are five types of statistics although the record formats for the various resources are always the same. First, there are the unsolicited statistics CICS writes when it deallocates a dynamic resource. For example, the statistics for an auto-installed terminal are written to SMF when it logs off and CICS deletes the definition. Second are end of day statistics written when CICS shuts down. Third are interval statistics recorded at whatever interval you set in the SIT.
In our shop we record interval records every hour. An important thing to note is that many of the statistic buckets get reset when the interval expires. The fourth and fifth types are requested statistics. Both types are written at the execution of an "EXEC CICS PERFORM STATISTICS RECORD" command or through CEMT. However, requested reset statistics include the RESETNOW operand which resets the buckets as is done with interval statistics.
As I said earlier, statistics record types are broken up along domain and resource management boundaries. Each statistic type is denoted by a numeric record identifier. In addition, some domains have both global and resource statistic records. For instance, for transaction manager there are global records listing region wide statistics such as the total number of transactions and the how often CICS hit max task (MXT). There are also resource level statistic records for every transaction defined on the system. Fortunately, assembler copy book DFHSTIDS in SDFHMAC lists each statistic type and its corresponding numeric ID. IBM supplies assembler copy books with the format and fields of each statistic type in SDFHMAC. As always, consult the IBM documentation for proper format, interpretation and use of the statistic fields. The Performance Guide is an excellent resource.
As you can imagine, this wealth of available information is not easy to get to. But once you get to it, it can be very valuable.
Check out other CICS tips here.