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IT30726: PURESCALE INSTANCE MAY PANIC WHEN UNFIXING A PAGE DUE TO AN INVALID PAGE LATCH

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APAR status

  • Closed as program error.

Error description

  • A Db2 pureScale instance may panic when releasing a page latch
    while a bufferpool decrease operation is running. The agent
    hitting the panic will see a similar message like the following
    in the db2diag.log:
    
    FUNCTION: DB2 UDB, SQO Latch Tracing,
    SQLO_SLATCH_CAS64::releaseConflict, probe:330
    MESSAGE :
    ZRC=0x870F011E=-2029059810=SQLO_LATCH_ERROR_EXPECTED_HELD
              "expected latch to be held."
    CALLED  : OS, -, unspecified_system_function
    DATA #1 : String, 39 bytes
    Attempting to unlock an invalid latch:
    DATA #2 : File name, 16 bytes
    sqloLatchCAS64.C
    DATA #3 : Source file line number, 8 bytes
    1054
    DATA #4 : Codepath, 8 bytes
    2
    DATA #5 : String, 125 bytes
    0x0000000000000000: {
       held X: 0
       reserved for X: 0
       shared holders: 0
       firstSharIndex: 0x0
       firstExclIndex: 0x0
    }
    DATA #6 : LatchMode, PD_TYPE_LATCH_MODE, 8 bytes
    0x0 (invalid mode)
    DATA #7 : String, 399 bytes
    {
       state         = 0x0000000000000000
                     = {
                           held X: 0
                           reserved for X: 0
                           shared holders: 0
                           firstSharIndex: 0x0
                           firstExclIndex: 0x0
                       }
       starve X mode = false
       xWaitCount    = 0
       requestCount  = 0
       identity      = SQLB_BPD::bpdLatch_SX (265)
    }
    DATA #8 : Pointer, 8 bytes
    0x0a000301f2bb58e0
    DATA #9 : Hexdump, 16 bytes
    0x0A000301F2BB58E0 : 0000 0000 0000 0000 C109 0000 0000 0000
    ................
    CALLSTCK: (Static functions may not be resolved correctly, as
    they are resolved to the nearest symbol)
      [0] 0x0900000037769678
    dumpDiagInfoAndPanic__17SQLO_SLATCH_CAS64CFCPCcCUiCUlT3ClT3CiT1T
    3T7 + 0x2F8
      [1] 0x090000003776AE4C releaseConflict__17SQLO_SLATCH_CAS64Fv
    + 0x10C
      [2] 0x0900000038D35DFC sqlbUnfixPage__FP11SQLB_FIX_CB + 0x9BC
      [3] 0x090000003A812728
    sqliUnFixPage__FP7SQLI_CBP14SQLI_PAGE_DESCiT3 + 0x108
      [4] 0x090000003A888F9C sqliwrap__FP7SQLI_CBiUi + 0x1DDC
      [5] 0x090000003A7EA254 sqlischd__FP7SQLI_CBP11SQLI_SDGLOBUsUi
    + 0x7D4
      [6] 0x090000003A7E3EBC
    sqlidelk__FP8sqeAgentP9SQLD_IXCBP10SQLI_IXPCRP8SQLD_KEY8SQLZ_RID
    UlP16SQLB_OBJECT_DESC + 0x12BC
      [7] 0x090000003ACCE400
    IPRA.$sqldUpdateIndexes__FP8sqeAgentP8SQLD_TCBP8SQLD_CCBP13SQLD_
    TDATARECP15SQLD_TDATAREC32T4T5PUcUl + 0x540
      [8] 0x090000003ACCA414
    sqldRowUpdate__FP8sqeAgentP8SQLD_CCBUlPP10SQLD_VALUET3PPv +
    0x1F94
      [9] 0x090000003E179DEC sqlriupd__FP8sqlrr_cb + 0x8CC
      [10] 0x090000003A8C2F38
    sqlriSectInvoke__FP8sqlrr_cbP12sqlri_opparm + 0x618
      [11] 0x0900000039938CE4
    sqlrr_process_execute_request__FP8sqlrr_cbib + 0x3644
      [12] 0x09000000398D2E40
    sqlrr_execute__FP14db2UCinterfaceP9UCstpInfo + 0x4A0
      [13] 0x090000003ECFE8BC
    sqljs_ddm_excsqlstt__FP14db2UCinterfaceP13sqljDDMObject + 0x5BC
      [14] 0x090000003EC7AEE0
    sqljsParseRdbAccessed__FP13sqljsDrdaAsCbP13sqljDDMObjectP14db2UC
    interface + 0x280
      [15] 0x090000003EC7DF64
    sqljsParse__FP13sqljsDrdaAsCbP14db2UCinterfaceP8sqeAgentb +
    0x2264
      [16] 0x090000003EC4913C
    IPRA.$sqljsSqlam__FP14db2UCinterfaceP8sqeAgentb + 0xE9C
      [17] 0x090000003EC51854
    sqljsDriveRequests__FP8sqeAgentP14db2UCconHandle + 0xB4
      [18] 0x090000003EC471F0
    IPRA.$sqljsDrdaAsInnerDriver__FP18SQLCC_INITSTRUCT_Tb + 0x13F0
      [19] 0x090000003EC44634
    sqljsDrdaAsDriver__FP18SQLCC_INITSTRUCT_T + 0x334
      [20] 0x090000003796B9A0 RunEDU__8sqeAgentFv + 0xB60
      [21] 0x0900000037945BC0 EDUDriver__9sqzEDUObjFv + 0x300
      [22] 0x0900000037827200 sqloEDUEntry + 0x360
      [23] 0x090000000055DE10 _pthread_body + 0xF0
      [24] 0xFFFFFFFFFFFFFFFC ?unknown + 0xFFFFFFFF
    
    The latch information in the stack file in the FODC directory
    will indicate the agent is holding a page latch in S mode but in
    a different address than the one logged in DATA #8 above.
    
    <LatchInformation>
    ...
    Holding latch type: (SQLO_LT_SQLB_BPD__bpdLatch_SX) - Address:
    (0xa000301f52e60a0), mode: S, Line: 1650, File: sqlbfix.C
    ...
    </LatchInformation>
    
    Before hitting the panic, there is a bufferpool reduce message
    in the db2diag.log for the specific bufferpool where the page
    resides, similar to the following:
    FUNCTION: DB2 UDB, buffer pool services, sqlbAlterBufferPoolAct,
    probe:90
    MESSAGE : Altering bufferpool "<bufferpool name>" From: "687820"
    <automatic> To:
              "675148" <automatic>
    

Local fix

  • Temporarily set the bufferpool to a fixed value instead of
    automatic if it was before.
    Do not run ALTER BUFFERPOOL SIZE statement to reduce a buffer
    pool size while some IUD workload is running.
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 11.1.4.5 or later                             *
    ****************************************************************
    

Problem conclusion

  • Upgrade to Db2 11.1.4.5 or later
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT30726

  • 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

    2019-10-28

  • Closed date

    2021-02-22

  • Last modified date

    2021-02-22

  • 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

[{"Line of Business":{"code":"LOB10","label":"Data and AI"},"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"}]

Document Information

Modified date:
27 February 2021