IBM Support

IT36093: DB2_FMP_COMM_HEAPSZ VALUES GREATER THAN 1GB NOT HONORED

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APAR status

  • Closed as program error.

Error description

  • If the DB2_FMP_COMM_HEAPSZ is set to greater than 1GB size (
    ~250,000 pages ), its silently set to a value of ~1GB.
    
    In highly concurrent environments where the FMP infrastructure
    is used extensively ( such as Federation ), this can cause "Out
    of memory" errors and subsequent crash of the FMP threads. This
    happens even when the registry var is set to a higher value than
    1GB.
    
    db2diag.log will show error below originating from db2agent and
    the heap being around 900 MB.
    
    FUNCTION: DB2 UDB, SQO Memory Management,
    sqloMemLogPoolConditions, probe:30
    DATA #1 : <preformatted>
    Out of memory failure for Undefined Heap on node 0.
    Requested block size           : 4202516 bytes.
    Physical heap size             : 964558848 bytes.
    Configured heap size           : 966393856 bytes. <=== 921 MB
    Unreserved memory used by heap : 0 bytes.
    Unreserved memory left in set  : 0 bytes.
    
    Alternative method to check size of DB2_FMP_COMM_HEAPSZ is to
    run Linux/Unix's "ipcs -a" to check shared memory segment size
    for fenced user id (db2fenc1).
    
    ipcs -a
    
    ------ Shared Memory Segments --------
    key        shmid      owner      perms      bytes      nattch
    0x00000000 1875673093 db2fenc1   601        966918144  111
    

Local fix

  • For Federated users only, this restores v11.1 behaviour and
    allows more concurrent Federeated routines (non-SQL stored
    procedure / user defined function) to be run. However on busy
    systems the Out Of Memory may still be encountered and thus
    recommendation is to apply IT36093.
    
    1) db2set DB2_FED_FMP_COMM_BUF_SIZE=15
    2) db2stop
    3) db2start
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * db2fmp used to run non-SQL routines                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Apply v11.5.6.0 to DB2 server                                *
    ****************************************************************
    

Problem conclusion

  • First fixed in v11.5.6.0
    

Temporary fix

  • See LOCAL FIX
    

Comments

APAR Information

  • APAR number

    IT36093

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    B50

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-03-02

  • Closed date

    2021-06-16

  • Last modified date

    2021-06-16

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

    IT21460

  • 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":"BU029","label":"Software"},"Product":{"code":"SSEPGG","label":"DB2 for Linux- UNIX and Windows"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"11.5"}]

Document Information

Modified date:
17 June 2021