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IC68267: Control dynamic downward adjustment of FCM resources

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • Customers with large DPF environments like are experiencing
    significant performance issues and
    apparent hangs due to contention when FCM resources are tuned
    automatically. The system
    controller thread (db2sysc) will adjust FCM resources downward
    after 30 minutes or more of low
    workload. During relatively quiet times, the resources can get
    adjusted down to very low values.
    This causes problems on systems with large workload bursts. When
    the workload increases dramatically,
    the FCM resources need to be adjusted upwards quickly and this
    is when performance issues due to latch
    contention in the dynamic adjustment code occurs. This problem
    gets worse on large DPF
    instances with many logical partitions configured.
    

Local fix

  • Large DPF customers can set FCM resources to large fixed values.
    However, the downside is that this may cause node failures in
    cases when db2fcmr/db2fcms EDUs run out of FCM buffers/channels.
    

Problem summary

  • Control dynamic downward adjustment of FCM resources
    

Problem conclusion

  • Customers with large DPF environments like are experiencing
    significant performance issues and
    apparent hangs due to contention when FCM resources are tuned
    automatically. The system
    controller thread (db2sysc) will adjust FCM resources downward
    after 30 minutes or more of low
    workload. During relatively quiet times, the resources can get
    adjusted down to very low values.
    This causes problems on systems with large workload bursts. When
    the workload increases dramatically,
    the FCM resources need to be adjusted upwards quickly and this
    is when performance issues due to latch
    contention in the dynamic adjustment code occurs. This problem
    gets worse on large DPF
    instances with many logical partitions configured.
    

Temporary fix

  • Upgrade to DB2 V9.7 FP3
    

Comments

APAR Information

  • APAR number

    IC68267

  • 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

    2010-05-01

  • Closed date

    2011-11-01

  • Last modified date

    2011-11-01

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

    IC66162

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

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSY

       UP



Document information

More support for: DB2 for Linux, UNIX and Windows

Software version: 9.7

Reference #: IC68267

Modified date: 01 November 2011