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OA56409: PERFORMANCE IMPACT DUE TO FAILURE TO OFFLOAD ZIIP/ZAAP WORKLOAD WHEN RUNNING HD=NO AND OA49692 PTF APPLIED 18/11/07 PTF PECHANGE

A fix is available

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APAR status

  • Closed as program error.

Error description

  • After installing the PTF for OA49692 (z/OS Supervisor z14
    support E3906/K ), a customer running with Hiperdispatch=NO
    in an environment where offloading of zIIP workload to a
    general CP was occurring noted a significant reduction in the
    amount of zIIP workload that was being offloaded to the general
    CP during periods of high zIIP usage.  This resulted in
    performance impact in the form of delays to zIIP-based
    workloads.
    
    zAAP workload is similarly affected by this error.
    
    Note that customers will only be impacted by this problem if the
    following conditions all exist:
    
    - Running with HD=NO ( hiperdispatch=no )
    - Running with PTF for OA49692 installed
    - Running with IIPHONORPRIORITY=YES or IFAHONORPRIORITY=YES
    - Running with zIIPs or zAAPs heavily loaded such that
      offloading to general CPs was occurring prior to installation
      of the PTF for OA49692.
       - NOTE: customers running ZAAPZIIP=YES with sufficient zAAP
         workload to require offloading will see this problem
         reflected as a significant reduction in offloading of zIIP
         workload.
    
    
    PE INFORMATION:
    
    USERS AFFECTED:  Customers running with the following
    environment:
    - Hiperdispatch = NO (HD=NO)
    - PTF for OA49692 applied   (PTF UA93156 for HBB77A0, PTF
      UA93148 for HBB77B0)
    - Running with IFAHONORPRIORITY=YES or IIPHONORPRIORITY=YES
    - Running with high zIIP or zAAP usage such that offloading of
      work to the general CP would be expected
    
    USER IMPACT:  APAR OA49692 added new function, but introduced an
    error in existing function.  Customers running in the specific
    environment described above may experience processing delays to
    zIIP- or zAAP-based workload during periods of heavy usage due
    to failure of general CPs to help the overloaded specialty
    engines.  For recommended action, please refer to the LOCAL FIX
    section of this APAR.
    
    
    
    VERIFICATION STEPS:
    
    1) The above 4 conditions:
        - HD=NO
        - PTF for OA49692 installed
        - IFAHONORPRIORITY=YES or IIPHONORPRIORITY=YES
        - offloading of zIIP or zAAP workload prior to installation
          of PTF for OA49692
    
       are met.  If further confirmation is required, continue with
       step 2.
    
    2) The significant reduction in offloading of zIIP or zAAP
       workload following installation of the PTF for OA49692 can be
       seen in a before/after comparison of:
    
       - RMF I CPU activity reports
       - affected jobs in the RMF III Processor Usage reports
       - ASCB-specific fields related to timing of work within the
         affected jobs, viewable in an SVC dump.  In particular the
         ASSB_TIME_ZIIP_ON_CP field at ASSB+x'258' (for zIIP
         workload) or the ASSB_TIME_IFA_ON_CP field at ASSB+x'1D8'
         (for zAAP workload) will be notably less (almost zero) in
         the "after" picture
    

Local fix

  • RECOMMENDATION
    
    Pre-COR closed PTFs are available and can be provided upon
    request up until the point of PTF closure.  COR closed PTFs are
    expected to be available within approximately 2 weeks of APAR
    closure.
    
    It is recommended that customers leave the PE PTF in place and
    take one of the following circumventive measures up until the
    time that the corrective PTF can be installed:
    
    - Stagger zIIP or zAAP workloads to reduce need for offloading
      to general CPs
    
    or
    
    - Run with HD=YES
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    *  Users running z/OS HBB77A0 and above,                       *
    *                 and IEAOPTxx HIPERDISPATCH=NO,               *
    *                 and running a heavy zIIP or zAAP workload    *
    *                     such that offloading to a general CP     *
    *                     occurs,                                  *
    *                 and with the following PTFs for OA49692      *
    *                     installed:                               *
    *                                                              *
    *                     UA93156                                  *
    *                     UA93148                                  *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    *  When running IEAOPTxx HIPERDISPATCH=NO                      *
    *                      and OA49692's PTFs installed,           *
    *                      performance degradation occurs due to   *
    *                      insufficient offloading of zIIP or      *
    *                      zAAP work to a general CP.              *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    Dispatcher processing does not properly offload zIIP or zAAP
    work to a general CP when IEAOPTxx HIPERDISPATCH=NO is
    specified.
    

Problem conclusion

  • Correct Dispatcher processing to properly offload zIIP or
    zAAP work to a general CP when IEAOPTxx HIPERDISPATCH=NO
    is specified.
    

Temporary fix

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

Comments

APAR Information

  • APAR number

    OA56409

  • Reported component name

    SUPERVISOR CONT

  • Reported component ID

    5752SC1C5

  • Reported release

    7A0

  • Status

    CLOSED PER

  • PE

    YesPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-10-29

  • Closed date

    2018-11-06

  • Last modified date

    2018-12-12

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

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

    UA97819 UA97820

Modules/Macros

  • IEAVEDS0
    

Fix information

  • Fixed component name

    SUPERVISOR CONT

  • Fixed component ID

    5752SC1C5

Applicable component levels

  • R7A0 PSY UA97820

       UP18/11/21 P F811 ­

  • R7B0 PSY UA97819

       UP18/11/21 P F811 ­

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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Document Information

Modified date:
12 December 2018