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OA44183: EXCESSIVE CPU CONSUMPTION IN *MASTER* DUE TO IAXUR RUNNING FOR PAGEABLE LARGE REFORM.

A fix is available

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APAR status

  • Closed as program error.

Error description

  • If a pageable large frame is broken up into 4K frames, some of
    those 4K frames can be used for long-term fixed frames owned by
    nonswappable address spaces.  If this happens and a later reform
    is attempted, this frame cannot be reformed, and IAXUR will
    reschedule itself every 5 seconds indefinitely.
    IAXUR should recognize this situation and stop attempting to
    reform nonreformable large pages.
    

Local fix

  • Apply PTF when available.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: Users of JBB778H and above.                  *
    ****************************************************************
    * PROBLEM DESCRIPTION: High CPU in *MASTER* address space      *
    *                      caused by IAXUR free frame SRB          *
    *                      continuously rescheduling itself        *
    *                      attempting to reform pageable large     *
    *                      frames.                                 *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Pageable large frames were broken up to satisfy real storage
    demand for 4k frames.  Later on, the system demand for 4k frames
    declined and these pages were scheduled to be reformed into
    pageable large frames.  Some of the frames scheduled for reform
    were fixed, requiring IAXUR to be scheduled to reclaim the
    allocated frames.  The address spaces that owned these frames
    were nonswappable and IAXUR scheduled itself to try again in 5
    seconds.  These frames remained fixed for a long period of time
    and IAXUR continuously rescheduled itself, causing high CPU in
    *MASTER* each time it ran.
    

Problem conclusion

  • Module IAXUR is changed to not reschedule itself when reforming
    pageable 1meg pages if the frames are fixed and the address
    spaces are nonswappable.
    

Temporary fix

  • *********
    * HIPER *
    *********
    

Comments

APAR Information

  • APAR number

    OA44183

  • Reported component name

    RSM - REAL STOR

  • Reported component ID

    5752SC1CR

  • Reported release

    790

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2014-01-09

  • Closed date

    2014-03-20

  • Last modified date

    2014-05-02

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

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

    UA72880 UA72881

Modules/Macros

  • IAXUR
    

Fix information

  • Fixed component name

    RSM - REAL STOR

  • Fixed component ID

    5752SC1CR

Applicable component levels

  • R78H PSY UA72881

       UP14/04/02 P F404 Ž

  • R790 PSY UA72880

       UP14/04/02 P F404 Ž

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.



Document information

More support for: z/OS family

Software version: 790

Operating system(s): MVS, z/OS

Reference #: OA44183

Modified date: 02 May 2014