PH19242: HUFFMAN COMPRESSION SUPPORT FOR DSN1COMP

Obtain the fix for this APAR.

APAR status

• Closed as program error.

Error description

• Enhance DSN1COMP to provide compression ratio estimation for
  Huffman compression and provide comparison to existing Fixed
  length compression.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All Db2 for z/OS V12 users of DSN1COMP                       *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * Enhance DSN1COMP to provide                                  *
  * compression ratio estimation for                             *
  * Huffman compression and provide                              *
  * comparison to existing Fixed                                 *
  * length compression.                                          *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * Apply corrective PTF when available                          *
  ****************************************************************
  Enhance DSN1COMP to support Huffman encoding estimation for
  uncompressed data.
  

Problem conclusion

• 1. The functionality of DSN1COMP utility is enhanced to
     provide data compression estimation using Huffman encoding.
     The compression estimation on space saving from DSN1COMP
     only applies to uncompressed table space which has remained
     unchanged.
  2. A new optional parameter, COMPTYPE, is added to the
     DSN1COMP utility. Valid values for COMPTYPE are FIXED,
     HUFFMAN, or ALL.
     Example control statements:
     - DSN1COMP,PARM='COMPTYPE(FIXED)'
     - DSN1COMP,PARM='COMPTYPE(HUFFMAN)'
     - DSN1COMP,PARM='COMPTYPE(ALL)'
     The COMPTYPE parameter is compatible with all other
     parameters that apply to Db2 data that resides in Universal
     Table Space (UTS). It is not compatible with parameters
     that apply specifically to Index or Lob table space.
     Any other value for COMPTYPE will produce the error message
  DSN1981I INVALID PARM FIELD: COMPTYPE
  3. If COMPTYPE parameter is NOT specified then DSN1COMP will
     provide compression estimation based on the current
     hardware. If the current hardware is z13 or earlier then
     only Fixed-length compression will be reported. If z14 or
     newer then both Fixed-length and HUFFMAN estimations will
     be in the report.
  4. DSN1940I message format has been enhanced for readability
     and the option to display both HUFFMAN and Fixed-length
     Db2 Data compression estimation.
  EXAMPLE 1:
  Job input:
  EXEC PGM=DSN1COMP,
       PARM='REORG,COMPTYPE(ALL)'
  Output:
  DSN1944I DSN1COMP INPUT PARAMETERS
              4,096  DICTIONARY SIZE USED
                  0  FREEPAGE VALUE USED
                  5  PCTFREE VALUE USED
                     COMPTYPE(ALL) REQUESTED
                     ESTIMATE BASED ON DB2 REORG METHOD
                255  MAXROWS VALUE USED
  DSN1940I DSN1COMP COMPRESSION REPORT
    Hardware support for Huffman compression is available
  +---------------------------------+--------+-------+----------+
  |                                 |  Un-   | Comp  | Compress |
  |                                 |compress| Fixed | Huffman  |
  +---------------------------------+--------+-------+----------+
  | Data (in KB)                    |  9,755 | 1,783 |      919 |
  | Percent savings                 |        |    81%|       90%|
  |                                 |        |       |          |
  | Average Bytes per row           |    914 |   169 |       88 |
  | Percent savings                 |        |    81%|       90%|
  |                                 |        |       |          |
  | Data Pages needed               |  2,739 |   530 |      256 |
  | Percent Data pages saved        |        |    80%|       90%|
  |                                 |        |       |          |
  | Dictionary pages required       |      0 |    16 |       20 |
  | Rows scanned to build dictionary|        |   234 |      234 |
  | Rows scanned to provide estimate|        |10,953 |   10,953 |
  | Dictionary Entries              |        | 4,096 |    4,080 |
  |                                 |        |       |          |
  | Total Pages (Dictionary + Data) |  2,739 |   546 |      276 |
  | Percent savings                 |        |    80%|       90%|
  +---------------------------------+--------+-------+----------+
  DSN1994I DSN1COMP COMPLETED SUCCESSFULLY, 2,733 PAGES PROCESSED
  5. DSN1COMP is corrected to print message ID DSN1138E, instead
     of DSN1138I, to indicate when incompatible parameters are
     specified.
  EXAMPLE 2 with incompatible parameters:
  input:
  EXEC PGM=DSN1COMP,PARM='COMPTYPE(ALL),LOB'
  output:
  DSN1138E DSN1COMP COMPTYPE AND LOB    CANNOT BOTH BE SPECIFIED
  DSN1993I DSN1COMP TERMINATED,               0  PAGES PROCESSED
  6. DSN1COMP for Huffman estimation does not require z14 or
     newer hardware, unlike Db2 main line process. However, it
     validates hardware requirement during the execution time.
  7. For more information about this enhancement, see the
     description of this APAR in the Db2 for z/OS documentation:
  https://www.ibm.com/support/knowledgecenter/en/SSEPEK_12.0.0/
  wnew/src/tpc/db2z_12_enhancements.html
  

Temporary fix

Comments

APAR Information

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

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

  UI69388

Modules/Macros

• DSN1COMP DSN1DCTV DSN1DCTE DSN1GDI  DSN1DCTI DSNUDCTC DSN1GDC
  DSN1GDV  DSN1PRNT DSN1DCTB DSN1GDB
  

Fix information

• Fixed component name

  DB2 OS/390 & Z/

• Fixed component ID

  5740XYR00

Applicable component levels

• RC10 PSY UI69388

     UP20/05/12 P F005

Fix is available

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