How WLM can influence DB2 for z/OS distributed thread performance
Paul Kenney 12000097KJ Visits (13482)
Are your DB2 threads getting enough resources? Are the Work Load Manager Enclave (WLM) definitions too restrictive?
If on the Enhanced 3270UI using the DB2® active threads summary (select 'T' from the Enterprise Summary) or the DB2 Thread Detail Accounting screen you see that the elapsed time for a distributed thread is greater than the threshold you have set (the plan name DISTSERV and the correlation ID starting with db2jcc_ indicates this is a distributed thread),
you can navigate to the DB2 Thread WLM Enclave Detail screen, select 'E' and that will display the enclave token being used by this thread as seen on the next screen shot.
Next, navigate to IBM Tivoli® OMEGAMON® XE on z/OS® Enhanced 3270UI All Active Sysplexes screen and enter 'S' in the selection field on the Sysplex that the DB2 is running on to get the LPAR overview for the Sysplex. You will then see a display of all the LPARs in this Sysplex.
Select 'N' in the selection field to see all the Enclave information from Work Load Manager on the LPAR that the DB2 subsystem is running on.
The Enclave Information by Token screen can be sorted by the Enclave Token or the Owning Jobname. For DB2 distributed threads, the owning job name is the DB2 subsystem name with DIST following. D91JDIST, for example, would be for DB2 subsystem D91J. You can then enter 'I' in the selection field to get Service Class Period information or 'S' to see Enclave Details.
Here you may see that the definition of this Enclave is not giving the DB2 thread enough resources and the definition needs to be revised. In this case, the performance index shows this service class is performing better than its goal.
A performance index of less than 1 indicates that the period is performing better than its goal. A performance index of 1 indicates the period is meeting its goal. A performance index greater than 1 indicates the period is performing worse than its goal.
This functionality is available with the OMEGAMON Performance Management Suite.