Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Running z/OS 1.6 with UA15128 applied, it is possible to get
  abend522's after message IWM063I is issued indicating the WLM
  policy was refreshed due to a processor speed change.  When
  processing the processor speed change, SRM is incorrectly
  calculating the invocation interval for IRARMMS6.  IRAEVSSI
  mistakenly multiplies the invocation interval by 1024, which
  results in the interval being much longer than it should be and
  IRARMMS6 not getting control as often as it should.  If the job
  wait time is shorter than the incorrectly calculated invocation
  interval for IRARMMS6, this results in jobs timing out with an
  ABEND522 because the ASCBEWST field is not being updated
  because IRARMMS6 is not getting control when it should.
  Additional Keywords:
       msgIWM063I
       D/T2084
       D/T2094
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of z/OS 1.6 (HBB7709) and          *
  *                 above.                                       *
  ****************************************************************
  * PROBLEM DESCRIPTION: Running z/OS 1.6 with UA15128 applied,  *
  *                      it is possible to get abend522's after  *
  *                      message IWM063I is issued indicating    *
  *                      the WLM policy was refreshed due to a   *
  *                      processor speed change.  When           *
  *                      processing the processor speed change,  *
  *                      SRM is incorrectly calculating the      *
  *                      invocation interval for IRARMMS6.       *
  *                      IRAEVSSI mistakenly multiplies the      *
  *                      invocation interval by 1024, which      *
  *                      results in the interval being much      *
  *                      longer than it should be and IRARMMS6   *
  *                      not getting control as often as it      *
  *                      should.  If the job wait time is        *
  *                      shorter than the incorrectly calculated *
  *                      invocation interval for IRARMMS6, this  *
  *                      results in jobs timing out with an      *
  *                      ABEND522 because the ASCBEWST field is  *
  *                      not being updated because IRARMMS6 is   *
  *                      not getting control when it should.     *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The following two problems can only occur if a processor speed
  change occurs while the system is running.  Dynamic processor
  speed changes are only supported on specific hardware like z/890
  and z/990.
  
  1. With z/OS release 1.7 (HBB7720), the unit of SRM seconds for
  scheduling of SRM and WLM algorithms was changed from milli
  seconds to micro seconds. This is for internal SRM and WLM use
  only.  Erroneously, this was partially rolled back into z/OS
  release 6 (HBB7709) and leads to the miscalculation of these
  fields:  MCCMS6L (interval of IRARMMS6), RMPTDLYD,
  RmctxSrmSecond.
  
  The value of all fields are too big by a factor of 1024.
  
  2. Additionally, the calculation of CCCFXSLF can be incorrect.
  This is true for z/OS releases 6 and 7 (HBB7709, HBB7720).
  Whether this happens depends on the speed of the CPU.  CCCFXSLF
  defines the number of instructions before a spin loop timeout
  condition is detected.  With faster CPUs the value can become
  larger than 31 bit.  To prevent an overflow, the CPU adjustment
  factor is checked and CCCFXSLF is capped at x'7FFFFFFF if the
  CPU adjustment factor is so small (i.e. fast cpu) that the
  calculated spin loop factor would be larger than a full word.
  The old value for the comparison was 16*1024 and at HBB7709 this
  was changed to 400.  IRAEVSSI was not updated with the new
  value.
  

Problem conclusion

• The above described problems were fixed in module IRAEVSSI which
  is called if a dynamic processor speed change occurs.
  
  1. MCCMS6L, RMPTDLYD, and RmctxSrmSecond will no longer be
  multiplied by 1024 and only be adjusted according to the speed
  change (HBB7709 only).
  
  2. CCCFXSLF will be set to x'7FFFFFFF when the CPU adjustment
  factor is less than 400.
  

Temporary fix

Comments

APAR Information

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

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

  UA19510 UA19511

Modules/Macros

• IRAEVSSI
  

Fix information

• Fixed component name

  5752 SYS RSRCE

• Fixed component ID

  5752SC1CX

Applicable component levels

• R709 PSY UA19510

     UP05/07/12 P F507

• R720 PSY UA19511

     UP05/07/12 P F507

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.

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Product categories:

Software

Operating System

z/OS family

APARs - z/OS environment

Operating system(s):

MVS, z/OS

Software version:

709

Reference #:

OA12155

IBM Group:

IBM Server Group

Modified date:

2005-11-23