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IT04946: IN CERTAIN CIRCUMSTANCES THE BFDEREFQUEUETHREAD THREAD CAN HOLD AN EXCESSIVE NUMBER OF LOCKS.

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APAR status

  • Closed as program error.

Error description

  • In certain circumstances, especially when a large number of
    files have been deleted, for example through expiration, the
    bfDerefQueueThread thread can hold an excessive number of locks.
    This can then cause database lock escalations.
    
    
    When lock escalations are occurring, there will be a noticeable
    slow down of the server performance. It is also likely that the
    active log space will begin filling as database transaction
    processing takes longer. This could cause a server outage if the
    log space fills.
    
    To see if you are affected by this problem, verify that there
    are 'LLM-memory low' messages and lock escalations messages in
    the db2diag.log file. For example:
    
    
    Locking memory management: LLM-memory low.
    Escalation threshold activated.
    LLM-lock list size = 148650000
    LLM-lock list available = 1936
    
    
    ADM5501I  DB2 is performing lock escalation. The affected
    application is named "dsmserv", and is associated with the
    workload name "SYSDEFAULTUSERWORKLOAD" and application ID
    "*LOCAL.tsminst1.140929162329"  at member "0". The total
    number of locks currently held is "3733", and the target
    number of locks to hold is "1866".
    

Local fix

  • Increase the DB2 LOCKLIST for the database.
    
    To find an appropriate value by which to increase the LOCKLIST,
    first run the commands below to find the count of dereferenced
    chunks per node/fsid in the BF_DEREFERENCED_CHUNKS table:
    
    $ db2 connect to tsmdb1
    $ db2 "select nodeid, fsid, count(*) from
    tsmdb1.BF_DEREFERENCED_CHUNKS group by nodeid, fsid" >
    bfdc_count.txt
    
    In the 'bfdc_count.txt' output file, find the largest value in
    the third column, which represents the number of dereferenced
    chunks for a node/fsid combination.
    
    Say for example that '40,000,000' is the largest number in that
    column. Also assume that each lock consumes 128 bytes of memory
    and that the LOCKLIST value represents the number of 4096-byte
    pages. Increase the LOCKLIST by a number sufficient to handle
    '40,000,000' by calculating as below. In this case you want to
    increase the LOCKLIST by 1,250,000-
    
    
    
    40000000 * 128 bytes / 4096 bytes = 1250000
    
    
    So if your current LOCKLIST is set to '500000', increase that
    number by 1250000 by setting a new LOCKLIST of 1750000.
    
    For steps to change the lock list in the database configuration,
    refer to the documentation at the link below-
    
    
    http://www-01.ibm.com/support/docview.wss?uid=swg21430874
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All Tivoli Storage Manager server users.                     *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See error description.                                       *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Apply fixing level when available. This problem is currently *
    * projected to be fixed in level 7.1.5. Note that this is      *
    * subject to change at the discretion of IBM.                  *
    ****************************************************************
    

Problem conclusion

  • This problem was fixed.
    Affected platforms:  AIX, HP-UX, Solaris, Linux, and Windows.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT04946

  • Reported component name

    TSM SERVER

  • Reported component ID

    5698ISMSV

  • Reported release

    71A

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2014-10-15

  • Closed date

    2016-02-04

  • Last modified date

    2016-02-04

  • 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

    TSM SERVER

  • Fixed component ID

    5698ISMSV

Applicable component levels

  • R71A PSY

       UP

  • R71H PSY

       UP

  • R71L PSY

       UP

  • R71S PSY

       UP

  • R71W PSY

       UP



Document information

More support for: Tivoli Storage Manager

Software version: 7.1.3

Reference #: IT04946

Modified date: 04 February 2016