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IT25666: MASTER MAINTENANCE PREPARE PHASE CODE UPDATE TO PREVENT POSSIBLE MISSING SUBSCRIPTIONS AND CACHE INCONSISTENCIES BETWEEN CPUS.

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • Errors AMQ9511 and AMQ9448 are logged along with FFST
    regarding ProbeID: RM220005 and Probe Type: MSGAMQ9511
    given by one or more slave repmans due to inconsistencies
    between CPUs regarding subscriptions in number and
    referenced object as well as expiration time.
    When multiple slaves are affected, in consequence the
    problem described in IT24388 may occur.
    This is a generic description of a multi root cause error
    scenario, please also check APARs about other problems
    identified: IT25665, IT25666, IT25669, IT25671.
    This APAR is about a general problem with the consistency
    of cluster cache maintenance, due to relying for multiple
    decisions on current usage state of object records
    in the cache.
    

Local fix

  • N/A
    

Problem summary

  • The information if a record is currently used by the
    queue manager is kept in shared memory, which is local
    for each CPU on NonStop.
    The maintenance operation on master were relying such
    decisions on the local cache state, not taking into account
    usage of entries on other CPUs. In consequence there have
    been problems due to missing subscriptions and cache
    inconsistencies between CPUs.
    

Problem conclusion

  • -
    Code was added to perform a maintenance prepare phase
    querying slave instances, to lock their cache and provide
    information about records currently in use.
    Maintenance was changed to also respect usage information
    from slaves, when ever decisions based on object usage are
    taken.
    Additionally each decision is recorded in the metadata.
    which is provided to the slaves along with the request
    to process, to ensure decisions being consistent for all
    cache instances. To guarantee correctness, slaves will
    hold lock of cluster cache until completing maintenance.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT25666

  • Reported component name

    WEBS MQ NSS ITA

  • Reported component ID

    5724A3902

  • Reported release

    531

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-07-12

  • Closed date

    2018-07-13

  • Last modified date

    2018-07-13

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

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

Fix information

  • Fixed component name

    WEBS MQ NSS ITA

  • Fixed component ID

    5724A3902

Applicable component levels

  • R531 PSY

       UP

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Document Information

Modified date:
27 September 2021