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PH34284: ABEND0C4 - REORG WITH INLINE STATISTICS ABEND IN DSNUSIDX OR DSNURWBR / POSSIBLE 00E2000E & DB2 CRASH UI71385 PTF PECHANGE

A fix is available

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APAR status

  • Closed as program error.

Error description

  • REORG with inline statistics causes overlay when the key is much
    larger than the mapping index with new code for parallel index
    rebuild.
    
    To trigger this error, the following conditions must be met:
    1) PH28092/UI71385 applied on the subsystem on which REORG runs
    2) REORG TABLESPACE SHRLEVEL CHANGE is run on a classic
    partitioned or PBR table space with exactly one
    partitioning+clustering index defined in it
    3) The partitioning+clustering index defined must have the sum
    of the key column lengths > 29 bytes
    4) The REORG is sorting the data records (SORTDATA YES) and is
    exploiting unload/reload partition parallelism (DSNU1160I
    issued)
    5) inline statistics is being collected on the PI, or the PI
    is a not-padded variable length index
    
    The problem is specific to the new parallel PI build in the
    unload/reload partition parallelism code path introduced by
    PH28092/UI71385. So turning off parallelism (by removing
    UTPRINT/SOFTDEVT or specifying DTPRIN01 data set..etc) can also
    avoid the problematic code path from being executed.
    
    Additional Symptoms:
    Abend0C4 DSNUSIDX +0127C
    Abend04E RC00C90101 DSNICMT2 :500D
    Abend04E RC00E2000D DSNSVSFB +00A58
    Abend04E RC00E2000E DSNSVSFB +00A40
    Abend04E RC00E40045 DSNUGSTA +024B4
    Abend0C4 DSNB1GET +0183A
    Abend0C4 DSNKLOD2 +01CB2
    CNK526E  DB2 SORT FOR Z/OS INTERNAL ABEND -   27
    

Local fix

  • 1. Add the following as 1st line of SYSIN to bypass PI build
       logic:
             DIAGNOSE TYPE(892)
    2. Disable Parallelism with PARALLEL 1 in REORG job
    

Problem summary

  • ****************************************************************
    * USERS AFFECTED:                                              *
    * All Db2 12 for z/OS users with PH28092 /                     *
    * UI71385 applied when REORG TABLESPACE                        *
    * SHRLEVEL CHANGE is run on a table space                      *
    * with a single clustering and partitioning                    *
    * index defined.                                               *
    ****************************************************************
    * PROBLEM DESCRIPTION:                                         *
    * REORG TABLESPACE SHRLEVEL CHANGE with                        *
    * unload reload partition parallelism                          *
    * resulted in a storage overlay with                           *
    * PH28092 / UI71385 applied.                                   *
    ****************************************************************
    * RECOMMENDATION:                                              *
    * Apply corrective PTF when available                          *
    ****************************************************************
    With PH28092 / UI71385 applied, a REORG TABLESPACE SHRLEVEL
    CHANGE using data unload/reload partition parallelism on a
    table space with a single clustering and partitioning index
    resulted in a storage overlay and caused Db2 to crash.  For
    this overlay to happen, the following conditions all need to
    be satisified after applying the erroring PTF:
    1. REORG TABLESPACE SHRLEVEL CHANGE is run on a classic
    partitioned or PBR table space with one and only one
    partitioning index defined on it
    2. The partitioning index defined must have the sum of the
    max key column lengths being greater than 29 bytes long, which
    is the size of the mapping index key
    3. REORG is sorting the data records (SORTDATA YES) and is
    exploiting unload/reload partition parallelism (DSNU1160I
    issued)
    4. Inline statistics is being collected on the index, or the
    index is a not-padded variable length index
    The reported problem is caused by incorrect program logic when
    the partitioning index is being built concurrently during data
    reload with partition parallelism.  REORG under allocates a
    storage buffer used for inline statistics and/or key conversion
    process when an index sort/build/stats task set is assigned
    both a PI partition and the mapping index to process, which ,
    happens when the degree of parallel index build is non-optimal
    with DSNU397I message issued.  The storage overlay happens
    when the trailing storage of this in-memory buffer is over-run
    and results in a variety of external symptoms:
    ABENDS0C4 DSNUSIDX +0127C OFFSET0127C
    ABEND04E RC00C90101 DSNICMT2 :500D ERQUAL500D
    ABEND04E RC00E2000D DSNSVSFB +00A58 OFFSET00A58
    ABEND04E RC00E2000E DSNSVSFB +00A40 OFFSET00A40
    ABEND04E RC00E40045 DSNUGSTA +024B4 OFFSET024B4
    ABEND0C4 DSNB1GET +0183A
    ABEND0C4 DSNKLOD2 +01CB2
    In addition to the storage overlay symptoms above, a part level
    REORG TABLESPACE in the same reported scenario might also
    encounter Db2 Sort error with CNK526E - DB2 SORT FOR Z/OS
    INTERNAL ABEND - 27, due to an incorrect/overlaid input
    parameter list being passed to the Db2 SORT program execution.
    The REORG utility failed with an ABEND04E RC00E40005 and
    RC00E40347 after Db2 Sort issued the internal error.
    Additional keywords:
    DB2OVRLAY/K  MSGDSNU1160I MSGDSNU397I
    

Problem conclusion

  • Code has been modified to correct the aforementioned problems
    related to REORG TABLESPACE execution on a range partitioned
    table space with a single clustering and partitioning index
    defined.
    

Temporary fix

Comments

APAR Information

  • APAR number

    PH34284

  • Reported component name

    DB2 OS/390 & Z/

  • Reported component ID

    5740XYR00

  • Reported release

    C10

  • Status

    CLOSED PER

  • PE

    YesPE

  • HIPER

    YesHIPER

  • Special Attention

    NoSpecatt / Xsystem

  • Submitted date

    2021-02-08

  • Closed date

    2021-03-04

  • Last modified date

    2021-07-15

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

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

    UI74269

Modules/Macros

  • DSNURBXD DSNURPCT
    

Fix information

  • Fixed component name

    DB2 OS/390 & Z/

  • Fixed component ID

    5740XYR00

Applicable component levels

  • RC10 PSY UI74269

       UP21/03/12 P F103 ­

Fix is available

  • Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.

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Document Information

Modified date:
16 July 2021