PI91168: CPSM WLM ROUTING MAY INCORRECTLY FAVOR SOME AORS WHEN THEY HAVE EQUAL LOADS

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• You use CPSM WLM to route work from routing regions ( TOR ) to
  target regions ( AOR ). All the AORs are equally favorable.
  That is, they have the same 'AOR Weight'. When this happens,
  CPSM should randomize the selection of equally favorable target
  regions so that the workload gets distributed as evenly as
  possible. Due to the way the randomization routine is currently
  designed, this may not always happen.
  .
  .
  Additional Symptom(s) Search Keyword(s): KIXREVSVR
  z14 upgrade2z14 D/T3906
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All CICSPlex SM V4R2M0 Users.                *
  ****************************************************************
  * PROBLEM DESCRIPTION: After upgrading to a z14 machine, CPSM  *
  *                      WLM routing distribution patterns from  *
  *                      routing regions running on the z14 may  *
  *                      appear different than on previous       *
  *                      machines.                               *
  *                                                              *
  *                      The different behavior will be more     *
  *                      apparent when using CPSM Sysplex        *
  *                      Optimized WLM processing.               *
  ****************************************************************
  * RECOMMENDATION: After applying the PTF that resolves this    *
  *                 APAR, all MASes running as CPSM WLM routing  *
  *                 regions must be recycled to pick up the new  *
  *                 code.                                        *
  ****************************************************************
  When a route request is received in a CPSM WLM routing region,
  it builds a list of all target regions that are in the scope of
  the route (Scope Vector), and associates a weight with each
  target region based upon task load, connection type and health
  factors, where the lower weight indicates the best available
  target region for the route.
  
  After building the Scope Vector, it is sorted low to high, and
  the target region with the lowest weight is selected for the
  route.  If more than one target region has the same lowest
  weight, then CPSM uses a randomization process to select one of
  the lowest weight tied target regions.
  
  This randomization process is performed by method EYU0WASV
  (WASV), and has been determined to be invalid for use with z14
  machine processing, resulting in some tied for lowest weight
  target regions getting more work than other regions.  The worse
  case scenario is when the same two target regions are tied for
  lowest weight.  In this situation, the same one will most likely
  be always chosen.
  
  While the randomization process does not work properly with z14
  machines in all situations, it is more likely to be evident when
  CPSM Sysplex Optimized WLM is in use, since the task load is a
  tiered value instead of an absolute value, which can keep a
  target region's load constant while it receives multiple routes.
  

Problem conclusion

• WASV has been updated to change the randomization process so
  that it works properly in z14 and earlier machines.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

  PI90941

• APAR is sysrouted TO one or more of the following:

  UI53573

Modules/Macros

• EYU0WASV
  

Fix information

• Fixed component name

  CICS TS Z/OS V4

• Fixed component ID

  5655S9700

Applicable component levels

• R70M PSY UI53573

     UP18/02/02 P F802 ¢

Fix is available

• Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.