A fix is available
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 number
PH19242
Reported component name
DB2 OS/390 & Z/
Reported component ID
5740XYR00
Reported release
C10
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2019-11-14
Closed date
2020-05-07
Last modified date
2020-06-01
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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Document Information
Modified date:
02 June 2020