IBM WebSphere Application Server Performance Cookbook

z/OS Recipes

  1. CPU core(s) should not be consistently saturated.
  2. Generally, physical memory should never be saturated and the operating system should not page memory out to disk.
  3. Input/Output interfaces such as network cards and disks should not be saturated, and should not have poor response times.
  4. TCP/IP and network tuning, whilst sometimes complicated to investigate, may have dramatic effects on performance.
  5. Consider tuning TCP/IP network buffer sizes.
  6. Collect and archive various RMF/SMF records on 10 or 15 minute intervals:
    1. SMF 30 records
    2. SMF 70-78 records
    3. SMF 113 subtype 1 (counters) records
    4. With recent versions of z/OS, Correlator SMF 98.1 records
    5. SMF 99 subtype 6 records
    6. If not active, activate HIS and collect hardware counters:
  7. Review ps -p $PID -m and D OMVS,PID=$PID output over time for processes of interest.
  8. Operating system level statistics and optionally process level statistics should be periodically monitored and saved for historical analysis.
  9. Review system logs for any errors, warnings, or high volumes of messages.
  10. Review snapshots of process activity, and for the largest users of resources, review per thread activity.
  11. If the operating system is running in a virtualized guest, review the configuration and whether or not resource allotments are changing dynamically.
  12. Use the Workload Activity Report to review performance.
  13. If there is sufficient network capacity for the additional packets, consider reducing the default TCP keepalive timer (TCPCONFIG INTERVAL) from 2 hours to a value less than intermediate device idle timeouts (e.g. firewalls).
  14. Review SYS1.PARMLIB (and SYS1.IPLPARM if used)
  15. Test disabling delayed ACKs

For details, see the z/OS and WAS traditional on z/OS chapters.