Support for compressing LOB data

Db2 12 supports compressing LOB data when zEnterprise® data compression (zEDC) hardware is available to the z/OS® environment. By compressing your LOB data, you can reduce the size of data in a LOB table space to ensure that the LOB table space and its associated base table space remain available for inserting data.

You can enable LOB compression for individual table spaces by specifying the COMPRESS YES option in a CREATE LOB TABLESPACE or ALTER TABLESPACE statement.

LOB data compression can also be enabled on all LOB table spaces that are associated with the Db2 directory. To enable LOB compression for the Db2 directory, set the COMPRESS_DIRLOB subsystem parameter to YES.

LOB compression requirements

The following conditions are required for LOB compression in Db2 for z/OS:
  • 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.