OA50777: JES2 HIGH CPU IN IAXIS AT HJE77A0

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• In HJE77A0 JES2 was changed to moved some of the data areas
  associated with CKPT processing from 31 to 64-bit storage.
  Correspondingly, JES2 also changed the way it creates and
  manages checkpoint versions (CKVR).
  
  Specifically, HASPCKVR makes use of IARVSERV CHANGEACCESS and
  SHARE  requests.  Due to the characteristics of the pages being
  shared, it is driving a large number of VIEWADD and VIEWDEL
  requests within IAXIS.  This causes an increase in CPU
  utilization within the JES2 address space.
  
  KNOWN IMPACT:
  Increased CPU utilization by the JES2 address space (within
  IAXIS module)
  
  VERIFICATION STEPS:
  1) Report monitors can show increased CPU utilization by JES2 at
     HJE77A0
  2) RSM IARVSERV ctrace run against JES2 address space will show
     a very large number of CHANGEACCESS entries followed by a
     very large number of VIEWDEL and VIEWADD entries
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of HJE77A0.                        *
  ****************************************************************
  * PROBLEM DESCRIPTION: JES2 checkpoint versions processing may *
  *                      unexpectedly consume a greater amount   *
  *                      of CPU in the JES2 address space.       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  In z/OS 2.2 JES2 (HJE77A0), when checkpoint data areas were
  moved from 31-bit to 64-bit storage, JES2 changed the way
  it creates and manages checkpoint versions:  Specifically,
  HASPCKVR, the Checkpoint Version Subtask, was changed to invoke
  the IARVSERV (RSM Virtual Storage Services) macro to perform
  CHANGEACCESS requests and additional SHARE requests.  Due to
  the characteristics of the pages being shared, these added
  requests resulted in an unexpected increase in the amount of
  processing performed by the IAXIS module, causing an increase
  in CPU utilization within the JES2 address space.
  

Problem conclusion

• TYPE/RESTART (HOT) IPL/REQUIRED (NO) CLPA (NO).
  
  Via RSM APAR OA50806, IARVSERV macro support has been changed
  to allow SHARE and UNSHARE operations against target virtual
  storage pages that may be read only.
  
  Using this new IARVSERV support, HASPCKVR, the Checkpoint
  Version Subtask, has been changed to remove IARVSERV
  CHANGEACCESS invocations that are no longer necessary preceding
  IARVSERV SHARE and UNSHARE invocations.  As a result of these
  changes, CPU utilization by HASPCKVR processing is
  significantly reduced.
  
  ****************************************************************
  *                                                              *
  *  For this APAR fix to be effective, the RSM APAR OA50806     *
  *  fix must also be applied.                                   *
  *                                                              *
  ****************************************************************
  
  APAR OA50777 prereq's (and sup's) for FMID HJE77A0:
  Pre's: * NONE *
  

Temporary fix

• *** * TEMPORARY FIX MAY BE OBTAINED FROM DLL OR INFO/ACCESS ****
  ******************* OA50777  DECK AVAILABLE ********************
  

Comments

APAR Information

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

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

  OA50806 UA82420

Modules/Macros

• HASPCKVR
  

Fix information

• Fixed component name

  JES2

• Fixed component ID

  5752SC1BH

Applicable component levels

• R7A0 PSY UA82420

     UP16/08/24 P F608

Fix is available

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