IBM Support

IT31700: APPLICATION MEMORY CONTINUALLY GROWS IN DPF ENVIRONMENTS AFTER UPGRADING TO RECENT FIX PACK LEVELS

Subscribe to this APAR

By subscribing, you receive periodic emails alerting you to the status of the APAR, along with a link to the fix after it becomes available. You can track this item individually or track all items by product.

Notify me when this APAR changes.

Notify me when an APAR for this component changes.

 

APAR status

  • Closed as program error.

Error description

  • A problem similar to a memory leak has been introduced in the
    following levels of code :
    10.1 Fix Pack 6 (APAR IT18654)
    10.5 Fix Pack 9 (APAR IT18655)
    11.1 Mod 1 Fix Pack 1 (APAR IT18656)
    11.5 GA
    
    Only DPF environments with long-running transactions are
    vulnerable. The memory buildup occurs when an SQL statement is
    repeatedly invoked without committing.
    On remote nodes only (not the coordinator), memory
    allocations associated with the SQL section are freshly
    allocated on each invocation instead of being reused.  Upon
    commit, however, the memory is released (cached for reuse or
    freed as part of normal cache fluctuations).
    
    There are several factors that point to this problem being the
    source of increased memory usage:
    
    1. The problem occurs after upgrading to the above-mentioned
    levels
    
    2. The memory usage is in the "Application Memory" consumer :
    
    db2pd -dbptnmem (ensure to run on remote partitions, eg. -member
    <partition number>)
    Name             Mem Used (KB) HWM Used (KB) Cached (KB)
    ========================================================
    APPL-TEST               160000        160000      157632
    
    db2 "select * from
    table(mon_get_memory_set('APPLICATION','TEST',-2))"
    will show increasing values for several columns, including
    MEMORY_SET_SIZE
    
    3. The specific memory pool that is increasing in memory usage
    is the "Application Shared" (APPL_SHARED) heap :
    db2 "select * from
    table(mon_get_memory_pool('APPLICATION','TEST',-2)) where
    MEMORY_POOL_TYPE='APPL_SHARED'"
    
    In db2pd this is the "appshr" pool in db2pd -db <db> -mempools
    output)
    
    4. specific memory blocks increasing are similar to the
    following :
    db2pd -db <db> -memblocks top appl 20
    Top memory consumers in Appl memory set:
    PoolID     PoolName   TotalSize(Bytes)     %Bytes TotalCount
    %Count LOC   File                 File hash code
    20         appshrh    555048               52.37  39
    14.39  5063  sqlra_sql_workspace.C  1095929873
    20         appshrh    86112                8.12   39
    14.39  1193  sqlriSectInit.C               1127556507
    20         appshrh    20592                1.94   39
    14.39  7550  sqlri_dss.C                    930532034
    20         appshrh    19968                1.88   39
    14.39  1556  sqlriSectInit.C               1127556507
    20         appshrh    4992                 0.47   39
    14.39  2490  sqlra_sql_workspace.C  1095929873
    20         appshrh    4680                 0.44   39
    14.39  1116  sqlriSectInit.C              1127556507
    
    5. Applications are seen with long-running transactions, eg. the
    following monitoring statement shows a very high number of
    activity requests within a unit of work :
    db2 "select uow_id,act_rqsts_total  from
    table(mon_get_unit_of_work(null,null)) order by act_rqsts_total
    desc"
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * DPF environments with long running transactions              *
    * at or above 11.1 Mod 1 Fix Pack 1                            *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * upgrade to DB2 Version 11.1 Mod 4 Fix Pack 6                 *
    ****************************************************************
    

Problem conclusion

  • Problem first fixed in DB2 Version 11.1 Mod 4 Fix Pack 6
    

Temporary fix

Comments

APAR Information

  • APAR number

    IT31700

  • 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

    2020-01-30

  • Closed date

    2021-03-17

  • Last modified date

    2021-03-17

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

    IT30681

  • 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