IBM Support

PH03837: HIGH PRIVATE STORAGE USAGE DUE TO K&T NOTIFICATIONS

A fix is available

Subscribe

You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • Queue managers in a QSG can exhibit high storage usage following
    a large number of K&T notifications from other queue managers in
    the QSG.
    .
    .
    Information from PH04105 that was closed as a duplicate of
    PH02959, the parent of this APAR:
    Abstract: OPTIMIZE USE OF MQ'S DXWB CONTROL BLOCKS TO PROVIDE
              STORAGE CONSTRAINT RELIEF IN SUBPOOL 229 KEY 7
    .
    DXWB control blocks for MQ represent an item of work from XCF
    that needs to be processed by MQ.
    
    There can be situations, such as a problem in XCF or DB2 or a
    problem with a looping or high volume application that can
    cause higher use of these control blocks.
    
    L3 has found a way to optimize use of the DXWBs to avoid or
    delay running out of storage related to these blocks.
    
    
    Additional Symptom(s) Search Keyword(s):
    
    Common symptoms associated with a high number of DXWB and EKTM
    control blocks:
    
    - The amount of free storage reported in CSQY220I decreases,
      perhaps suddenly, and the message becomes more frequent:
        CSQY220I Queue manager is using mm MB of local storage, nn
                 MB are free
    
    - Eventually storage may run out:
        CSQY221I Queue manager is short of local storage
        CSQY222E Queue manager is critically short of local storage
                 - take action
    
    - ABENDS5C6 occurs with reason codes such as 00E2000B
    
    - ABEND878-00000010
    
    Queue Sharing Group QSG
    878 S878 S0878 ABEND878 ABENDS878
    Subpool 229 Key 7   SP229 KEY7 K7  private storage
    

Local fix

  • - For BATCH and RRSBATCH applications, consider setting
      CONNSWAP=NO in CSQ6SYSP to prevent MQ applications from MQI
      being swapped out in the middle of an MQI call. This will-up
      avoid contention that may lead to a build-up of the
      control blocks.
    
    - Search for APARs relating to DXWB blocks:
      https://ibm.biz/BdXXKn
    
    - Check the syslog for errors with XCF (IXLnnnn), DB2
      (DSNnnnn), IMS (DFSnnnn), or MQ (CSQnnnn) that may prevent
      normal operation. For instance, the thread in MQ that
      processes the DXWBs may be hung due to a problem in DB2:
        DSNJ111E OUT OF SPACE IN ACTIVE LOG DATA SETS
    
    - Check logrec to see if any prior abends may have interrupted
      normal processing. See sample JCL at
     http://www.ibm.com/support/docview.wss?rs=171&uid=swg21291812
    
    - Review whether a looping application may be causing the
      Coupling Facility (CF) to be flooded with requests
    .
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED: All users of IBM MQ for z/OS Version 9       *
    *                 Release 0 Modification 0 and Release 1       *
    *                 Modification 0.                              *
    ****************************************************************
    * PROBLEM DESCRIPTION: Abend S878, storage exhaustion and      *
    *                      abnormal queue manager termination can  *
    *                      occur when a large number of XCF        *
    *                      messages are received from other        *
    *                      queue managers in the queue sharing     *
    *                      group.                                  *
    ****************************************************************
    When messages arrive over XCF, the queue managers XCF
    message/group exits obtain a DXWB control block to contain the
    message, and queue it for processing by the XCF worker task.
    If a large number of messages arrive (for example due to
    messages arriving on shared queues with TRIGTYPE(EVERY) ),
    the number of DXWBs waiting to be processed grows, and the
    storage allocated for these control blocks can result in private
    storage shortages and S878 abends.
    This is exacerbated by unoptimal use of this storage, leading to
    more storage being allocated than is required, and storage
    fragmentation.
    

Problem conclusion

  • The use of DXWBs is changed to use more appropriately sized
    storage areas, reducing the storage requirement for this
    processing.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH03837

  • Reported component name

    IBM MQ Z/OS V9

  • Reported component ID

    5655MQ900

  • Reported release

    000

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2018-10-10

  • Closed date

    2018-11-13

  • Last modified date

    2019-10-07

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

    PH02959

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

    UI59656 010PC2Ÿ UI59657 010PC2Ÿ

Modules/Macros

  • CSQ5GRX0 CSQ5MGX0 CSQ5RCMQ CSQ5STRT CSQ5XWK1 CSQSIQCP
    

Fix information

  • Fixed component name

    IBM MQ Z/OS V9

  • Fixed component ID

    5655MQ900

Applicable component levels

  • R000 PSY UI59656

       UP18/12/14 P F812 ¢

  • R100 PSY UI59657

       UP18/12/15 P F812 ¢

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.

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSYHRD","label":"IBM MQ"},"Component":"","ARM Category":[],"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"9.0","Edition":"","Line of Business":{"code":"LOB36","label":"IBM Automation"}}]

Document Information

Modified date:
07 October 2019