Formula for TCB-CPU-TOT FIELD
Article ID: 15301
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Issue/Introduction
How is the Sysview Performance Management Option for Db2 for z/OS (IDB2) TCB-CPU-TOT IQL field derived from SMF fields?
Would like to know the specific formula. The reason for the question is that have migrated from IBM Omegamon PE SMF metrics
to use IDB2 SMF offloaded data and see discrepancies in Class1 CP CPU data. Specifically, the Class1 CPU reported via
IDB2 is always higher than Omegamon. Class1 elapsed time and Class2 elapsed and CPU time practically show no discrepancies.
Resolution
For non-rollup threads TCB-CPU-TOT=(QWACEJST-QWACBJST)+QWACSPCP+QWACUDCP
For rollup threads TCB-CPU-TOT=QWACEJST+QWACSPCP+QWACUDCP
According to IBM Knowledge Center for OMEGAMON XE for DB2 Performance Expert on z/OS:
CLASS 1: MVS TCB TIME
The amount of MVS CPU time used. If the time cannot be calculated or the value is negative, N/C is printed in this field.
Calculated from the Db2 field QWACEJST - QWACBJST.
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