PM79773: EXCESSIVE NUMBER OF RLS DEADLOCKS WHEN MULTIPLE CHANGE.DBDS COMMANDS ARE PROCESSED IN PARALLEL

A fix is available

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APAR status

  • Closed as program error.

Error description

  • When running a vendor RELOAD utility for several areas in the
    same DEDB, an excessive number of MSGIGW10077I messages occurred
    indicating deadlocks.  This occurred during the step that issued
    a CHANGE.DBDS DB() AREA() ICON command.
    .
    
    If several CHANGE.DBDS for DBDSs that are in the same full
    function or HALDB or for the same AREAs that are in or AREA
    deadlocks can occur when attempting to update the DB record in
    RECON.  If enough jobs are involved this can lead to an unending
    set of deadlocks and retries.  This is in part because the
    CHANGE.DBDS processing gets the DB record with a share level
    lock and then, if it is determined an update is needed for that
    record, it will get an exclusive lock before doing the update.
    If two jobs do this at the same time, I deadlock occurs.  If
    several jobs are involved we can get into a situation were all
    the jobs eventually become the deadlock victim and then retry.
    This can continue endlessly
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All V11 IMS DBRC PRA user will be affected.  *
    ****************************************************************
    * PROBLEM DESCRIPTION: Excessive number of RLS deadlocks when  *
    *                      multiple CHANGE.DBDS commands are       *
    *                      processed in parallel.                  *
    ****************************************************************
    * RECOMMENDATION: INSTALL CORRECTIVE SERVICE FOR APAR/PTF      *
    ****************************************************************
    When running a vendor RELOAD utility for several areas in the
    same DEDB, an excessive number of MSGIGW10077I messages occurred
    indicating deadlocks. This occurred during the step that issued
    a CHANGE.DBDS DB() AREA() ICON command.
    
    If several CHANGE.DBDS for DBDSs that are in the same full
    function or HALDB, or the several AREAs in the same DEDB,
    deadlocks can occur when attempting to update the DB record in
    RECON. If enough jobs are involved, this can lead to an unending
    set of deadlocks and retries. This is in part because the
    CHANGE.DBDS processing gets the DB record with a share level
    lock and then, if it is determined an update is needed for that
    record, it will get an exclusive lock before doing the update.
    If two jobs do this at the same time, a deadlock occurs.  If
    several jobs are involved we can get into a situation where all
    the jobs eventually become the deadlock victim and then retry
    and this will continue endlessly.
    

Problem conclusion

  • GEN:
    KEYWORDS:
    
    *** END IMS KEYWORDS ***
    DSPURI60 is changed to issue a slightly different message if the
    retry error was hit for a IDALKADD request. It will issue the
    DSP1190 message with a 'LKADD' request type if that was the last
    request. Also, if it was a timeout for LKADD, only issue the
    message every 25 times instead of every 5 times.
    
    DSPPRAB is changed to add a new message threshold constant
    PRAB_MSGTHOLD_LKADD used to special case timeout errors for the
    IDALKADD request.
    
    DSPURM60 was changed to get an EXclusive lock on the DSPRLOCT
    calls for DB and AAUTH records.
    
    DSPUSTB2 defines new MSGDSP1190.
    
    ================================================================
    GC18971302
    -
    THE FOLLOWING TEXT DESCRIBES THE DOC CHANGE:
    -
    A new DBRC message is obtained for this apar. Please use the
    following text description for the new DBRC MSGDSP1190W.
    
    DSP1190W A request to obtain a VSAM lock on a record has
    timed out nnnn times.
    
    Explanation
    
     An attempt by DBRC to obtain a VSAM lock for serialization
     purposes has repeatedly timed out. A lock request might time
     out repeatedly for one of the following reasons:
    
     *DBRC instances from multiple IMS systems are performing
      similar actions, such as might occur when a large number
      of utilities are running in parallel.
    
     *A DBRC instance is processing a long-running request, such
      as a LIST.RECON command.
    
    System Action
    
     Processing continues.
    
    System programmer response
    
     Issue the DISPLAY SMS,URID(ALL) command to determine if a DBRC
     instance is holding a lock for an excessive amount of time. If
     one is, consider cancelling that job. If the timeouts are not
     caused by one of the previously listed reasons, collect a dump
     from all DBRC instances and call IBM support.
    

Temporary fix

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

Comments

APAR Information

  • APAR number

    PM79773

  • Reported component name

    IMS V11

  • Reported component ID

    5635A0200

  • Reported release

    100

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-12-27

  • Closed date

    2013-03-01

  • Last modified date

    2013-04-02

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

    PM79367

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

    UK92134

Modules/Macros

  •    DSPURI60 DSPURM60 DSPUSTB2
    

Publications Referenced
GC18971302        

Fix information

  • Fixed component name

    IMS V11

  • Fixed component ID

    5635A0200

Applicable component levels

  • R100 PSY UK92134

       UP13/03/13 P F303

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


More support for:

IMS

Software version:

100

Reference #:

PM79773

Modified date:

2013-04-02

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