IBM Support

IT38375: Shared memory segments grow without limit in some MQ usage scenarios

Subscribe to this APAR

By subscribing, you receive periodic emails alerting you to the status of the APAR, along with a link to the fix after it becomes available. You can track this item individually or track all items by product.

Notify me when this APAR changes.

Notify me when an APAR for this component changes.

 

APAR status

  • Closed as program error.

Error description

  • Operating system shmall limit may be reached, leading to
    errno=28 (ENOSPC) from shmget(), and MQ FDC files are written
    reporting this condition.
    
    Example:
    
    Probe Id          :- XY132002
    Component         :- xstCreateExtent
    Program Name      :- amqzlaa0
    Probe Description :- AMQ6119S: An internal IBM MQ error has
    occurred (Failed to get memory segment: shmget(0x00000000,
    162623488) [rc=-1errno=28] No space left on device)
    Arith2            :- 28 (0x1c)
    Comment1          :- Failed to get memory segment:
    shmget(0x00000000, 162623488) [rc=-1 errno=28] No space left on
    device
    
    Also, the ipcs -a output shows 10s of shared memory segments of
    size approximately 160 MB, owned by mqm.
    

Local fix

  • The time to hit the shmall limit will be greater if the shmall
    limit is raised.
    The default for shmall on many systems is 8 GB.  Raise this to
    16 GB to increase the time to failure.
    However, if the queue manager is having this problem then there
    is no permanent workaround, you must install the fix.
    

Problem summary

  • ****************************************************************
    USERS AFFECTED:
    This issue is more likely to be observed on queue managers which
    frequently unload queues (when there are no input or output
    handles remaining against those queues) which have a variety of
    messages sizes.
    
    
    Platforms affected:
    MultiPlatform
    
    ****************************************************************
    PROBLEM DESCRIPTION:
    When unloading a queue from memory, some small data blocks were
    not being marked as free for re-use.
    

Problem conclusion

  • The IBM MQ code has been corrected to ensure that these small
    blocks are marked for re-use.
    
    ---------------------------------------------------------------
    The fix is targeted for delivery in the following PTFs:
    
    Version    Maintenance Level
    v9.1 LTS   9.1.0.11
    v9.2 LTS   9.2.0.5
    v9.x CD    9.2.5
    
    The latest available maintenance can be obtained from
    'WebSphere MQ Recommended Fixes'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
    
    If the maintenance level is not yet available information on
    its planned availability can be found in 'WebSphere MQ
    Planned Maintenance Release Dates'
    http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
    ---------------------------------------------------------------
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT38375

  • Reported component name

    IBM MQ BASE MP

  • Reported component ID

    5724H7271

  • Reported release

    910

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-09-15

  • Closed date

    2022-01-13

  • Last modified date

    2022-01-21

  • 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

    IBM MQ BASE MP

  • Fixed component ID

    5724H7271

Applicable component levels

[{"Line of Business":{"code":"LOB45","label":"Automation"},"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"910"}]

Document Information

Modified date:
22 January 2022