Configuring the Application Trace Facility FASTMON user exit

FASTMON is a user exit type introduced in IMS V15.1, as a high-performance alternative to the IMSMON type. The purpose of FASTMON is to significantly reduce the CPU overhead on monitoring IMS compared to IMSMON. The function of FASTMON is identical to that of IMSMON, except the fact that FASTMON is a Type-1 exit and therefore is not refreshable. Although both types are still supported, FASTMON is the preferred method when no REFRESH capability is required. The FASTMON exit module KOIMONF0 should be used instead of KOIMON00.

About this task

Note:
  • The following PTFs are required to enable this feature: APAR OA60851, APAR PH24963 for IMS V15.1
  • This procedure applies only to IMS V15.1 and above environments. Skip the procedure if you have IMS V14 or previous environments.

Procedure

Complete the following steps to configure the ATF component for IMS V15.1 and above environments:

  1. Install the ATF FASTMON user exit routine KOIMONF0.

    The load module KOIMONF0 can be found in the rtehilev.RKANMODR load library. Add this library to the STEPLIB concatenation of the IMS Control Region JCL.

  2. Configure IMS PROCLIB member DFSDFxxx.

    Add the FASTMON user exit definition to the IMS PROCLIB member DFSDFxxx:

    <SECTION=USER_EXITS>
EXITDEF=(TYPE=FASTMON,EXITS=(KOIMONF0))

    If the IMSMON user exit (KOIMON00) is already defined, either delete or comment out the EXITDEF statement.

Results

To activate the FASTMON user exit, IMS recycle is required, because it’s not refreshable type.

The following messages are issued:

  • in the IMS Control Region:

    KI2A0011I ATF FASTMON EXIT LOADED FOR IMSID=<imsID>

  • in an OMEGAMON for IMS Classic address space:

    KI2A0030I ATF FASTMON EXIT FOUND: <exit header info> AT <address>

Performance tips
  • When using ATF in high-workload environments (for example, Production), it is recommended to specify the trace option ‘Summarize Only = YES’ in order to minimize resource consumption (CPU, storage, DASD space), unless a detailed trace is necessary.
  • Use filters and exceptions to eliminate unwanted transactions from traces and thus reduce the overhead.
  • Stop ATF during periods when there are no active users and no tracing is needed. This will prevent unnecessary calls to the ATF FASTMON exit and thus reduce CPU overhead.
  • Ensure that the z/OS Service Class performance parameters for the OMEGAMON Classic started task are no lower than that of IMS.