IBM Support

IT27044: DB2 MAY HANG IN ACCESSING GLFH FILE WHEN USING MULTIPLE CONCURRENT IMPORT IN DPF

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APAR status

  • Closed as program error.

Error description

  • Import is using the SYSIBMADM.DBCFG interface to get config
    parameter values from all partitions just in case the db config
    is not the same on all partitions in DPF environment , so the
    selecting from SYSIBMADM.DBCFG broadcast the request to all
    nodes to get data. When all nodes got the request, they all need
    to access GLFH file each will acquire latch and then lock the
    file.  When multiple concurrent Import all query at the same
    time, this may cause massive contention on the same file lock,
    and db2 may hang there .
    
    we will see repeat invoking of statement like :
    SELECT SUBSTR(value, 1, 20) FROM SYSIBMADM.DBCFG WHERE name =
    CAST('decflt_rounding'    AS VARCHAR(15))
    
    Also we can see from  db2pd -api that both last sql statement
    and current sql statment is same selecting from SYSIBMAMD.DBCFG
    
     AnchID StmtUID    NumEnv     NumVar     NumRef     NumExe
    Text
    873    1087       1          1          364        364
    SELECT SUBSTR(value, 1, 20) FROM SYSIBMADM.DBCFG WHERE name =
    CAST('decflt_rounding'    AS VARCHAR(15))
    621    7502       1          1          366        366
    SELECT VALUE FROM SYSIBMADM.DBCFG WHERE NAME =
    'varchar2_compat'
    
    The stack will be like :
    
    
    _syscall6(0xfffffffcec3ebb20,0xffffffff7eaa91f0,0x2,0xffffffffff
    ffffff,0xfffffffcec3eb9c4,0x1002f4360) + 0x20
    
    __pos4obj_unlink(0xfffffffcec3ebb20,0xffffffff7eaa91f0,0x2,0xfff
    fffffffffffff,0xfffffffcec3eb9c4,0x1002f4360) + 0x24
      sem_open(0xfffffffcec3ebb20,0x0,0x0,0x1593d4,0x0,0x0) + 0x3dc
    
    __1cSOSSHIPCSemaphoreExGcreate6MkpknbCOSSIPCSemaphoreExCreatePar
    am__I_(0xfffffffcec3ec0d8,0xfffffffcec3ec0a8,0x0,0x4b5400,0xffff
    ffffffffffff,0xfffffffcec3ebb21) + 0x250
    
    __1cVsqlnlsGetCCInfoFromCC6FL_pknPsqlnls_cc_table__(0xfffffffcec
    3ecf98,0x0,0x40001,0xfffffffcec3ec218,0x1b0,0xfffffffcec3ec0d8)
    + 0x3a50
    
    sqloNLCKUnlock(0xfffffffcec3ecf98,0xfffffffcec3fffff,0x4f40634,0
    x3632800,0x40001,0x40000) + 0x244
    
    __1cMSQdDLP_GLFH_CBGunlock6M_i_(0xfffffffcec3ecf70,0xffffffff665
    7d870,0x4e07f4c,0x18800000,0x40000,0x3632b28) + 0x80
    
    __1cOsqlpgCloseGLFH6FpnMSQdDLP_GLFH_CB__i_(0xfffffffcec3ecf70,0x
    0,0x4e192dc,0x3632800,0xffffffff62f4ad48,0x40000) + 0xe4
    
    __1cTsqlpBuildParmsNoDPS6FpknIsqeAgent_pkc4iIIpIII5pnNSQdDLP_LH_
    PARMS__i_(0x0,0xfffffffcec3f3168,0x201752861,0x1,0x3,0xfffffffce
    c3effc8) + 0x694
    
    __1cIsqlpglhu6FpknIsqeAgent_pkc4iIIpIII5pnNSQdDLP_LH_PARMS__i_(0
    x0,0x201752861,0x0,0x0,0xfffffffcec3f3ec0,0x0) + 0x580
    
    __1cIsqlfgtlp6FIpvpI1pkcpc_i_(0x2,0x0,0xfffffffcec3f3ec4,0xfffff
    ffcec3f3ec0,0x201752861,0xfffffffcec3f3fec) + 0x12c
    
    __1cYsqlfInitDbCfgParamForGet6Fpc00kipnLdb2CfgParam_pnKsqlf_dbcf
    d_pnFsqlca_ipnQsqeLocalDatabase__i_(0xfffffffcfdb0bff0,0x0,0x70,
    0xffffffff60a1c0b5,0x1000,0x201752968) + 0x350
    
    __1cMsqlfGetDbCfg6FpnQsqeLocalDatabase_pnGdb2Cfg_ipnFsqlca__i_(0
    x201750080,0xfffffffcec3fc318,0x201752861,0x202899368,0x40000,0x
    0) + 0x96c
    
    __1cQsqlrwGetDBConfig6FpnIsqlrr_cb_pnUsqlrwGetDBConfigArgs_ppvpl
    _i_(0xffffffff7516a420,0xffffffff365623f0,0xfffffffcec3fc4f8,0xf
    ffffffcec3fc4f0,0x0,0x0) + 0x128
    
    __1cbEsqlrwGetWLMTableFunctionResult6FpnIsqlrr_cb_pnUsqlrw_rpc_t
    f_request_ppvplb_i_(0xffffffff7516a420,0xffffffff365623f0,0xffff
    fffcec3fc4f8,0xfffffffcec3fc4f0,0xffffffff5e882bb0,0x70) +
    0x48c
    

Local fix

  • Reduce the IMPORT concurrency
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 11.1 Mod 4 Fixpack 5 or higher                *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 11.1 Mod 4 Fixpack 5
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT27044

  • 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

    2018-11-20

  • Closed date

    2020-01-16

  • Last modified date

    2020-01-16

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

    IT25793

  • 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

  • RB10 PSN

       UP

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

Document Information

Modified date:
16 January 2020