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IT19994: SCA SEARCH AND INSERT LOGIC CAN LEAD TO A PERFORMANCE BOTTLENECKFOR AN XA WORKLOAD

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You can track all active APARs for this component.

 

APAR status

  • Closed as program error.

Error description

  • In a pureScale system with a high XA transaction workload, there
    is a possible performance bottleneck in the existing SCA search
    and insert logic.  This APAR has been opened to address that
    issue and devise a better workflow to help alleviate thie
    potential bottleneck.
    
    Formatting is a little messy, but from the CF monitoring you
    will see a significant value for the request time element for
    the ReadCastoutClass compared to the other calls:
    
    =============================================================
    CF-side command execution counts and average response times
    =============================================================
    
    select d.id, cast(substr(cf_cmd_name,1,50) as varchar(50)) as
    cf_cmd_name, total_cf_requests, decimal( (total_cf_requests /
    double(total_total_cf_requests)) * 100, 5, 2 ) as
    pct_total_cf_cmd, decimal( double(total_cf_cmd_time_micro) /
    total_cf_requests, 15, 2 ) as avg_cf_request_time_micro from
    mon_get_cf_cmd_diff as d, ( select id, sum(total_cf_requests) as
    total_total_cf_requests from mon_get_cf_cmd_diff group by id )
    as c where d.total_cf_requests > 0 and d.id = c.id order by id
    asc, total_cf_requests desc with UR
    
    ID     CF_CMD_NAME
    TOTAL_CF_REQUESTS    PCT_TOTAL_CF_CMD AVG_CF_REQUEST_TIME_MICRO
    ------ --------------------------------------------------
    -------------------- ---------------- -------------------------
       128 MessageResponseBlock
    5945551            34.73                      1.06
       128 ProcessSetLockState
    3824254            22.34                      2.23
     (...)
       128 WriteAndRegisterMultiple
    234652             1.37                     99.02
       128 ReadCastoutClass
    222867             1.30                    718.28 <==
       128 CrossInvalidate
    222353             1.29                      8.99
       128 ReadSetLFS
    75930             0.44                      1.70
       128 ReadAndRegister
    21980             0.12                      3.14
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 11.1 Mod 2 Fix Pack 2 or higher               *
    ****************************************************************
    

Problem conclusion

  • First fixed in DB2 11.1 Mod 2 Fix Pack 2
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT19994

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2017-03-31

  • Closed date

    2017-06-27

  • Last modified date

    2017-06-27

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

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

    IT21591

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEPGG","label":"Db2 for Linux, UNIX and Windows"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"11.1","Line of Business":{"code":"LOB10","label":"Data and AI"}}]

Document Information

Modified date:
29 June 2020