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COMPRESS DB2 DIR LOBS field (COMPRESS_DIRLOB subsystem parameter)

The value of the COMPRESS_DIRLOB subsystem parameter specifies whether LOB table spaces in the Db2 directory are to be compressed.

This subsystem parameter is new in Db2 12. It can be set at any function level, but it takes effect only after activation of function level 500 or higher.

Acceptable values: NO, YES
Default: NO
Data sharing scope: Same setting recommended on all members
Online changeable: Yes
Update: option 1 on panel DSNTIPB
DSNZPxxx: DSN6SPRM COMPRESS_DIRLOB
NO
LOB table spaces in the Db2 directory are not compressed. This is the default value.
YES
LOB table spaces in the Db2 directory are compressed the next time they are reorganized.
In a data sharing environment, all members should use the same setting for the COMPRESS_DIRLOB parameter. The result of a table space reorganization will be determined by the value of the COMPRESS_DIRLOB parameter on the member that executes the REORG TABLESPACE utility.
Important: Start of changeCompressing the LOB table spaces in the directory requires the following conditions to be met:
  • Db2 12 must be at function level 500 or higher.
  • The zEDC hardware and software must be available and configured in the z/OS system. For more information, see Requirements for zEnterprise Data Compression.

    In data sharing, system performance can degrade dramatically if a member accesses compressed LOB data and the zEDC hardware and software are not configured in z/OS.

  • The LOB table space must be associated with a base table that is in a universal table space.
  • The total length of the entire LOB must be larger than the defined data page size, otherwise the LOB is not compressed.
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