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IC96902: PERFORMANCE DEGRADATION OF HADR PRIMARY MAY OCCUR AFTER UPGRADING THE STANDBY TO V9.7 FP6 OR LATER FIXPAK.

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APAR status

  • Closed as program error.

Error description

  • After upgraded the HADR Standby to v9.7 FP6 or later fixpak, a
    performance degradation of HADR Primary may occur.
    
    From db2pd -hadr on Standby side, one problem can be observed
    that Standby is using almost 0% of receive buffer,
    2013-10-09-15.52.21.000999
       PrimaryFile  PrimaryPg  PrimaryLSN
       S0467575.LOG 26092      0x00004758AE52CC46
    
       StandByFile  StandByPg  StandByLSN         StandByRcvBufUsed
       S0467575.LOG 26091      0x00004758AE52BFAA 0%
    
    And from trace collection of EDU db2hadrs on Standby side, the
    hdrAddLogFiles function will take more time to complete the log
    initialization and specially opening log file is direct i/o -If
    logging disks are slow, then in this direct i/o case, the
    performance will be impacted.
    
    581182  exit DB2 UDB oper system services sqloopenp cei
    (2.3.15.825.2)
            pid 5636136 tid 200465 cpid 4850536 node 0 sec 14 nsec
    105142410
            codepath = 2:11:15:16:20:46:48:49
    
            rc = 0
            bytes 16
    
            Data1   (PD_TYPE_SQO_FILE_HDL,8) File handle:
      File Handle              = 518
      File System Block Size   = 0 bytes
      File System Type         = UNKNOWN
      File Handle Flags :
        Require Sector Align   = No
        DIO/CIO Mode           = Yes
        Raw Block Device       = No
        Reserved Handle        = No
        Flush On Close         = Yes
        Thread-Level Lock      = No
        Write-through Mode     = No
        File Not Tracked       = No
    
    Slower disk operation will adds up to a case that db2hadrs on
    Standby is busy with I/O manipulation for log initialization,
    during this time db2hadrs will not response any request from
    HADR Primary, therefore, HADR Primary may see performance
    degradation if db2hadrs spent longer time to initialize the log.
    

Local fix

  • Set a registry variable DB2_LOGGER_NON_BUFFERED_IO=OFF on HADR
    Standby to get back the  file system cache performance, however
    the side effect of DB2_LOGGER_NON_BUFFERED_IO=OFF is that it
    will enable all normal log operations to use File System Cache
    as well, this will incur overhead of File System Cache
    Management and side performance effect, specially after takeover
    the new primary will be impacted.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL USERS                                                    *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to v9.7 FP9 or use the local fix as workaround.      *
    ****************************************************************
    

Problem conclusion

  • This problem has been fixed in v9.7 FP9
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC96902

  • 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

    2013-10-14

  • Closed date

    2013-12-17

  • Last modified date

    2013-12-17

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

  • 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 PSN

       UP



Document information

More support for: DB2 for Linux, UNIX and Windows

Software version: 9.7

Reference #: IC96902

Modified date: 17 December 2013