The results from DFHLSCU will vary depending upon the values passed on SYSIN, and on the journal record activity found on the target log.
DFHLSCU divides up the target log into time segments according to the INTERVAL parameter. It analyses the log records found in each segment and determines which is the busiest segment, based on this logging activity. This segment is then used to determine the parameters for your logstream definitions and space requirements.
A system log from a CICS® system with a consistent workload will have a reasonably regular time period between activity keypoints. Conversely, a system log from a CICS system with irregular workloads, that rise and fall in no consistent way, or which rise to a peak then drop back to a low level, or else which rise to a plateau for a period of time before dropping back once more, will all result in varying time periods between activity keypoints.
Since DFHLSCU bases its calculations upon the time period which contains the busiest workload (that is, which generated most log records), the INTERVAL parameter will have a potentially marked effect upon the results generated by the utility if the CICS run which produced the target log had an inconsistent workload. For example, consider a target log from a ten hour CICS run. During that run, the system was lightly used for all but a one hour plateau near the middle of the run, when the workload rose rapidly to a much higher value, and many CICS log records were generated during that hour.
If DFHLSCU were run against such a log, with an INTERVAL parameter of considerably greater time than the duration of this plateau, then the results produced by the utility would be misleading. This is since DFHLSCU has to average the effect from each time segment, and the segments will span part of the plateau and also parts of the surrounding periods of low workload.
A general guide to specifying a value for the INTERVAL parameter is as follows. Firstly, study the workload of the CICS run which generated the target log for the utility. If the workload is reasonably consistent with no large peaks, troughs or plateaus, differing values for INTERVAL should have a limited effect. However, if the workload varies considerably, determine the duration of the busiest period of the CICS workload and specify an INTERVAL parameter of half this value. In this way, DFHLSCU should divide the log into time segments such that one segment should reside completely within a time period of consistently busy log activity. For the example with a one hour busy period given above, this methodology yields an INTERVAL value not greater than thirty minutes.
The recommendation is that DFHLSCU be run against a journal or set of journals that were produced from a single CICS region. DFHLSCU then outputs recommended values for structure sizing based on that CICS region. If the structure is intended to accommodate logstreams from more than one CICS region, the recommended approach is to run DFHLSCU against journals from each individual CICS region, and then sum the sizing recommendations from each output to determine the final structure sizing requirements.
If DFHLSCU is run against a target journal that was defined with FORMAT=SMF, an IEC036I 002-04 abend occurs when the first record is read. This is because DFHLSCU does not support analysis of target journals in SMF format.
If you want the target journal to be directed to a log stream when migrating to CICS Transaction Server for z/OS®, Version 3 Release 1, you must redefine it under CICS/ESA so that it does not use SMF formatting. Run a typical workload against the redefined journal before using DFHLSCU to produce a report for it.
If you want the target journal to be directed to SMF when migrating to CICS Transaction Server for z/OS, Version 3 Release 1, DFHLSCU does not give any benefit so do not use it against the SMF-format journal.
Unlike CICS/ESA, CICS Transaction Server for z/OS, Version 3 Release 1 does not support the journaling of SMF-format log data to non-SMF media (that is, the CICS Log Manager does not write records in SMF format to a log stream).