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IT35082: High CPU and decreased performance with high concurrency of index creation (on TEMP TABLES)

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APAR status

  • Closed as program error.

Error description

  • Db2 by default uses compression for indexes on created/declared
    temporary tables (CGTTs/DGTTs) and this behavior cannot be
    explicitly disabled, that is, there is no possibility to use
    "COMPRESS NO" keyword.
    
    Index compression entitlement is checked during index creation
    and requires serialization via a latch (mutex).
    If indexes are created with a very high concurrency the
    performance of that operation can be affected and CPU usage on
    the system will increase. This typically happens with scenarios
    involving indexes on declared/created temporary tables that have
    indexes defined.
    A backtrace of Db2 engine threads (EDUs) collected during the
    issue with a debugger/profiler or "db2pd -stack" will show a
    call stack with the following functions near the top:
    
    ossLockGetConflict
    NetlsRequestLicense
    LicGetAccessKey
    sqllcRequestAccess
    sqloSqlcRequestAccess
    sqloLicRequestAccess
    sqldIndexType
    sqldIndexCreate
    sqlrlRecreateSingleIndex
    sqlrlRecreateIndexObject
    sqlrlRecreateIndexes
    
    This APAR will address the behaviour by removing the license
    check for index compression on temporary tables.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * all                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to 11.5.6                                            *
    ****************************************************************
    

Problem conclusion

  • Upgrade to 11.5.6
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT35082

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B50

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2020-11-27

  • Closed date

    2021-06-11

  • Last modified date

    2021-06-11

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

    IT35021

  • 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

  • RB50 PSN

       UP

[{"Business Unit":{"code":"BU058","label":"IBM Infrastructure w\/TPS"},"Product":{"code":"SSEPGG","label":"DB2 for Linux- UNIX and Windows"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"11.5","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
17 December 2021