IC94323: LATCH PROTOCOL ISSUE IN ZIG ZAG JOIN EXECUTION LEADING TO DEADLATCH BETWEEN SUBAGENTS

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • This problem is similar to apar IC91168.
    
    The problem will manifest itself as 2 subagents for one
    statement deadlatching themselves on 2 internal latches.
    This can easily be identified by running db2pd -latches which
    may show :
    
    db2pd -latches shows :
    
    Latches:
    Address            Holder     Waiter     Filename
    LOC        LatchType            HoldCount
    0x0700000030CD7BD8 20049      20563      sqlpsvpt.C
    207        SQLO_LT_SQLP_SAVEPOINTS__spLatch 1
    0x07000000201F0128 20563      20049
    /view/db2_v101fp2_aix64_s121127_special_30486/vbs/engn/include/s
    qldinlines.h 8574       SQLO_LT_SQLD_APP_CB__inDMSlatch 1
    
    The names of the latches :  SQLO_LT_SQLP_SAVEPOINTS__spLatch and
    SQLO_LT_SQLD_APP_CB__inDMSlatch are important here
    and you will see that the holder and waiter are reversed for the
    2 latches.
    
    Collecting stack information via db2pd -stack all will show
    these 2 subagents with the following stacks:
    
    Subagent 1 is in sqldRowInsert requesting the inDMS latch,
    holding the SavePoint latch.
    
    getConflictComplex
    getConflict
    sqldRowInsert
    sqlrinsr
    sqlriisr
    sqlriSectInvoke
    
    Subagent 2 is in sqldBeginIndexCreate  requesting the SavePoint
    latch, holding the inDMS latch.
    
    sqlpGetSPLatch
    sqlpSpReq
    sqldBeginIndexCreate
    sqlriCreateTempTableIndex
    sqlriCreateIndexedTempTable
    sqlritib2
    sqldDataFetch
    sqliScanLeaf2NoLocking
    sqlifnxt
    sqlirdk
    sqldIndexFetch
    sqldRowFetch
    sqlritaSimplePerm
    sqlriZZOpenDims
    sqlriZZInit
    sqlriZigZagJoin
    

Local fix

  • To avoid this problem, the usage of the Zig Zag join , join
    strategy can be disabled by running :
    
    db2set DB2_REDUCED_OPTIMIZATION="ZZJN OFF"
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * all                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade the database server to V10.1 Fix Pack 4              *
    ****************************************************************
    

Problem conclusion

  • This problem has first been fixed in V10.1 Fix Pack 4
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC94323

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    A10

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2013-07-23

  • Closed date

    2014-06-26

  • Last modified date

    2014-06-26

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

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

    IC98144

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • RA10 PSN

       UP



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Document information


More support for:

DB2 for Linux, UNIX and Windows

Software version:

10.1

Reference #:

IC94323

Modified date:

2014-06-26

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