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IT35216: OOM: REQUEST MEMORY IS FAILING UNNECESSARILY EARLY WHEN THERE ISCONTENTION TRYING TO STEAL MEMORY FROM OTHER CONSUMERS

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APAR status

  • Closed as program error.

Error description

  • DB2 may report out of memory (OOM) errors even if there is
    sufficient cached database memory available.
    OOMs could probably have been avoided altogether if the request
    for Instance Memory (requestMemory) tried a bit harder to
    reclaim cached memory in the other consumers.
    
    For example, db2diag.log shows:
    
    2017-07-17-10.12.13.088021+000 I929503368E1120       LEVEL:
    Warning
    PID     : 10598                TID : 46970232104704  PROC :
    db2sysc 21
    INSTANCE: db2inst1             NODE : 021            DB   :
    BLUDB
    APPHDL  : 0-27126              APPID:
    10.113.34.46.62106.170717100710
    AUTHID  : ELTUSER              HOSTNAME: host
    EDUID   : 369804               EDUNAME: db2agntcol (BLUDB) 21
    FUNCTION: DB2 UDB, SQO Memory Management,
    SqloMemController::requestMemory, probe:50
    MESSAGE : ZRC=0x8B0F0000=-1961951232=SQLO_NOMEM "No Memory
    Available"
              DIA8300C A memory heap error has occurred.
    DATA #1 : String, 36 bytes
    OOM - Instance memory request failed
    DATA #2 : String, 35 bytes
    Logging disabled until next success
    DATA #3 : unsigned integer, 8 bytes
    34406400
    DATA #4 : unsigned integer, 8 bytes
    10
    DATA #5 : String, 13 bytes
    APPL-BLUDB
    DATA #6 : unsigned integer, 8 bytes
    1439105024
    DATA #7 : unsigned integer, 8 bytes
    0
    DATA #8 : unsigned integer, 8 bytes
    32124362752
    DATA #9 : unsigned integer, 8 bytes
    32131727360
    DATA #10: unsigned integer, 8 bytes
    3226992640
    
    ...
    APPL-BLUDB    - Current size : 1405376 KB, HWM : 2827136 KB,
    Cached : 0 KB
    DBMS-db2inst1 - Current size : 156096 KB, HWM : 162880 KB,
    Cached : 0 KB
    FMP_RESOURCES - Current size : 768 KB, HWM : 22528 KB, Cached :
    0 KB
    PRIVATE - Current size : 167040 KB, HWM : 340608 KB, Cached : 0
    KB
    FCM_RESOURCES - Current size : 104312 KB, HWM : 197376 KB,
    Cached : 0 KB
    DB-BLUDB    - Current size : 29537856 KB, HWM : 30081408 KB,
    Cached : 3184960 KB
    
    
    The typical db2diag.log entry will show "10" for the
    retryCounter value, which is DATA#4:
    The request size is DATA #3, 34MB
    APPL memory size is DATA #6, 1.4GB, not unreasonable.  DATA #7
    is its cached amount, 0.
    Limit is DATA #9, 32GB, DATA #8 shows usage we are at the limit
    But DATA #10 shows 3.2GB Cached, plenty to satisfy a 32MB
    request, and from subsequent entries we could see it´s all in
    Database Memory.
    So we can conclude we were hitting contention trying to reduce
    (the cached/overflow amount) in database memory set.
    It must be busy due to sort memory growth and/or decrease across
    the various sort pools.
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * ALL                                                          *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to Db2 Version 11.1 Mod 4 Fix Pack 6.                *
    ****************************************************************
    

Problem conclusion

  • First fixed in Db2 Version 11.1 Mod 4 Fix Pack 6.
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT35216

  • 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

    2020-12-09

  • Closed date

    2021-03-16

  • Last modified date

    2021-03-16

  • 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:
18 March 2021