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IC69045: GLOBAL SNAPSHOTS MAY CONSUME A LARGE AMOUNT OF FCM BUFFERS

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APAR status

  • Closed as program error.

Error description

  • In a multipartition environment, a large amount of FCM buffers
    can be consumed by large global snapshots. One example of such
    large global snapshots is, "db2 get
    snapshot for locks on <dbname> global" when there are many
    locks currently being held in the database.
    
    db2pd -fcm hwm output would show a single application
    consuming a lot of buffers
    

Local fix

  • The work around of setting DB2_MAX_GLOBAL_SNAPSHOT_SIZE should
    help to prevent a single snapshot from consuming all FCM
    buffers. Multiple concurrent large snapshots would still be a
    problem though.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * DPF environments                                             *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * Global snapshots collect monitoring information from all     *
    * database partitions and aggregate the result at the          *
    * coordinating partition. FCM buffers are required to send and *
    * receive the monitoring information. The coordinating         *
    * partition can consume a large number of FCM buffers          *
    * equivalent to the size of the entire snapshot result.  If    *
    * the database manager runs out of FCM buffers then node       *
    * failure is invoked to remedy the situation. This could lead  *
    * to applications receiving -1229 errors or losing connection  *
    * to the database.                                             *
    *                                                              *
    * Note that monitoring tools like db2top issue global          *
    * snapshots.                                                   *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 9.7 FP4 or later                              *
    ****************************************************************
    

Problem conclusion

  • As of DB2 9.7 FP4, global snapshots will not consume a large
    
    number of FCM buffers.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC69045

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    970

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2010-06-07

  • Closed date

    2011-04-25

  • Last modified date

    2011-04-25

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

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

    IC75870

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R950 PSN

       UP

  • R970 PSN

       UP

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Document Information

Modified date:
25 April 2011