IC82029: ACTIVATE DATABASE ON LINUX MAY INTERMITTENTLY FAIL WITH SQL1084 OR SQL1478

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You can track all active APARs for this component.

APAR status

  • Closed as program error.

Error description

  • In rare scenarios, database activation or first connect may fail
    intermittently with SQL1084 or SQL1478 due to the requirement to
    allocate multiple shared memory segments in a contiguous address
    range.
    
    On UNIX, DB2 typically allocates the initial database memory
    configured size as a single shared memory segment.  In special
    cases, such as encountering the 256GB shared memory segment
    maximum on Linux, the initial allocation may be broken up into
    multiple smaller segments, which must be attached in a
    contiguous address range.  It cannot be assumed that a
    contiguous address range of the required size will always be
    available based on the address assigned to the first segment by
    the operating system.
    
    It is unlikely that database activation (with multiple shared
    segments) will fail directly after db2start as the db2sysc
    process address space has little fragmentation.  A possible
    scenario could involve multiple databases, where a database with
    a very large (eg. > 256GB) database memory footprint is
    deactivated (without shutting down the instance), and a second
    database is activated which is assigned some of the address
    range previously used by the very large footprint database.
    Upon reactivation, the memory for the very large database may
    try to get assigned to the remainder of the range, which would
    fail if there is some object or allocation mapped at the top of
    the range.
    
    Other possible scenarios exist, but again only in combination
    with the special case of an operating system limit preventing a
    single shared memory segment being used for the initial database
    memory allocation.
    
    Note that RHEL6 and SLES 11 use a top-down process address space
    layout.  It is a known problem that allocating a database memory
    size > 256GB will always fail in these environments - see APARs
    IC79948/IC79934 (9.7 FP6, 9.5 FP9 respectively).  The APARs will
    solve the basic problem of allocating contiguous segments in a
    top-down address layout model, but not the rarer intermittent
    conditions addressed by this APAR.
    

Local fix

  • Any of:
    - recycle the instance with db2stop;db2start
    - limit database memory size to 250GB on Linux (allow a small
    amount of overhead to stay below the 256GB limit)
    - use "huge pages" on Linux for Database Memory
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * Linux systems with database memory configurations exceeding  *
    * 256GB                                                        *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * See Error Description                                        *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Upgrade to DB2 Version 9.7 Fix pack 7                        *
    ****************************************************************
    

Problem conclusion

  • problem first fixed in DB2 Version 9.7 Fix Pack 7
    

Temporary fix

Comments

APAR Information

  • APAR number

    IC82029

  • Reported component name

    DB2 FOR LUW

  • Reported component ID

    DB2FORLUW

  • Reported release

    970

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2012-03-14

  • Closed date

    2013-04-01

  • Last modified date

    2013-04-01

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

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

    IC85660

Modules/Macros

  • sqo
    

Fix information

  • Fixed component name

    DB2 FOR LUW

  • Fixed component ID

    DB2FORLUW

Applicable component levels

  • R970 PSN

       UP



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Document information


More support for:

DB2 for Linux, UNIX and Windows

Software version:

9.7

Reference #:

IC82029

Modified date:

2013-04-01

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