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OA50777: JES2 HIGH CPU IN IAXIS AT HJE77A0

A fix is available

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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 number

    OA50777

  • Reported component name

    JES2

  • Reported component ID

    5752SC1BH

  • Reported release

    7A0

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    YesSpecatt / Pervasive / Xsystem

  • Submitted date

    2016-06-27

  • Closed date

    2016-08-08

  • Last modified date

    2016-09-02

  • 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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Document information

More support for: z/OS family

Software version: 7A0

Operating system(s): MVS, z/OS

Reference #: OA50777

Modified date: 02 September 2016