Setting the size of the z/OS trace tables

When you set up your IMS system for diagnostics, you need to consider your settings for z/OS® trace tables as well.

z/OS system trace table

The z/OS system trace table is valuable for a large variety of problem types. The system trace table is page-fixed storage, and the default size is only 64 KB. You must ensure that there are enough real page frames for this specification.

Set z/OS system trace table size to 999 KB by issuing the z/OS command TRACE ST,999K in the z/OS COMMNDxx member of the SYS1.PARMLIB data set.

See z/OS MVS™ System Commands for more information.

z/OS master trace table

The master trace table maintains the most recently issued operator messages. It provides a view of external events at the time of failure. Ensure that the master trace table is large enough to span most error time frames. The default size is only 24 KB, which allows approximately 336 messages. A 500 KB specification allows approximately 7000 messages.

The master trace uses Subpool 229 Key 0 High Private Pageable Storage of the master scheduler address space.

Set the z/OS master trace table size to 500 KB by specifying the command TRACE MT,500K in the SCHEDxx member of the SYS1.PARMLIB data set.

See z/OS MVS Diagnosis: Tools and Service Aids, z/OS MVS Initialization and Tuning Reference, and z/OS MVS System Commands for complete details.