IMS Monitor

The IMS Monitor collects data while the online IMS subsystem is running. It gathers information for all dispatch events and places it, in the form of IMS Monitor records, in a sequential data set. Use the IMSMON DD statement in the IMS control region JCL to specify the IMS Monitor data set.

IMS adds data to this data set when you activate the IMS Monitor using the /TRACE command. The IMS MTO can start and stop the IMS Monitor to obtain snapshots of the system at any time. However, the IMS Monitor adds to system overhead and generates considerable amounts of data.

Control of IMS Monitor output

Plan to run the IMS Monitor for short intervals and to control its operation carefully. Shorter intervals also prevent the overall averaging of statistics, so that problems within the system can be more readily identified. The output of the IMS Monitor can be constrained by:

  • Type of activity monitored
  • Database or partition or area
  • Dependent region
  • Time interval

IMS Monitor output data sets

The IMS Monitor output can be either a tape or a DASD data set. Using DASD eliminates the need to have a tape drive allocated to the online system. If you want to use the IMS Monitor frequently, you might find that permanently allocated space for a DASD data set is convenient. One technique is to code DISP=SHR on the IMSMON DD statement so that the reports can be generated as each IMS Monitor run completes.

You must coordinate the report generation with the operator because each activation of the IMS Monitor writes over existing data. Although this overwriting does not occur for tape data sets, new volumes must be mounted. The volume is rewound, and a mount request is issued each time you start the IMS Monitor.

Recommendations:
  • Do not catalog IMS Monitor data sets. The IMS Monitor can produce multiple output volumes while IMS is running if the data sets are not cataloged.

    If you want IMS to dynamically allocate the IMS Monitor data set, do not include the IMSMON DD statement in the IMS control region JCL.

  • Allow IMS to dynamically allocate IMS Monitor tape data sets. A tape drive is not permanently reserved for the control region for dynamically allocated data sets.

IMS Monitor traces

After you establish monitoring requirements, you might be able to restrict the scope of the IMS Monitor activity. Restricting the scope has the advantage of reducing the impact of the IMS Monitor on system throughput. However, do not compromise the collection of useful data.

You can control what specific types of events are traced by using specific keywords on the /TRACE command. For example, you can monitor line activity, scheduling and termination events, activity between application programs and message queues, activity between application programs and databases, or all activity. You can also limit monitoring to:

  • Particular databases, partitions, or areas
  • Particular dependent regions
  • A specified interval of time

IMS Monitor reports

You can obtain reports based on the IMS Monitor output by using the IMS Performance Analyzer for z/OS® or the IMS Monitor Report Print utility (DFSUTR20).

The IMS Monitor Report Print utility summarizes and formats the raw data (except Fast Path data) produced by IMS and presents the information in a series of reports. You can suppress the reports pertaining to DL/I calls and tabulated frequency distributions.

The duration of the monitored events is determined by the entries for start and stop of the IMS Monitor. You cannot select a different time period for reporting, because many of the timed events are not captured continuously: only when the IMS Monitor is started and stopped. For this reason, ensure that the IMS Monitor is stopped before taking any action to stop the IMS control region.