CPU Time

SMF record types 4, 5, 30, 32, 34 and 35 have fields that contain the job and job step CPU times. This topic summarizes the different times that are included and those that are excluded in these CPU-time fields. This topic lists a few examples of some of the major causes of CPU-time variation between different runs of the same job or job step.

Job step CPU time is the amount of time devoted by the central processing unit to the processing of instructions for a given job step. Job CPU time is the sum of job step CPU times for all of the steps in a given job. CPU timing is done on an address space basis. The accumulation of CPU time is separated into processing time under TCBs and processing time under SRBs.

Note: If you want to account for CPU time for a single TCB or SRB (rather than a whole address space), use either the TIMEUSED. Do not use a store CPU timer (STPT) instruction, which can cause incorrect (such as negative) values. Use TIMEUSED either under a TCB or an SRB. See the z/OS MVS Programming: Authorized Assembler Services Reference SET-WTO for more information on the TIMEUSED macro.