CompressPermPrimaryCLOBDBs - Advanced SQL Engine - Teradata Database

Database Utilities

Advanced SQL Engine
Teradata Database
Release Number
July 2021
English (United States)
Last Update
Product Category
Teradata Vantage™

Specifies conditions under which MANUAL tables have the data blocks (DBs) of LOB permanent data that is eligible for compression in their primary data subtables compressed by default.

MANUAL tables are those created or altered to have BLOCKCOMPRESSION=MANUAL, or those with BLOCKCOMPRESSION=DEFAULT when the DefaultTableMode DBS Control field is set to MANUAL.

Compression is subject to the BlockLevelCompression field setting, and to the criteria specified by the MinPercentCompReduction and MinDBSectsToCompress DBS Control fields. DBs not meeting these minimum criteria will not be compressed.

Field Group


Valid Settings

Setting Description
ALWAYS The DBs of a new table will be compressed regardless of Query Band options specified at load time.
ONLYIFQBYES The DBs of a new table will not be compressed unless a Query Band used at load time specified to compress them.
UNLESSQBNO The DBs of a new table will be compressed unless a Query Band used at load time specified not to compress them.
NEVER The DBs of a new table will not be compressed regardless of any Query Band used at load time. The Ferret utility COMPRESS command will have no effect.



Changes Take Effect

After the DBS Control Record has been written.

Usage Notes

BLC enables data compression at the data block (DB) level of the Teradata file system. Compression reduces the amount of storage required for a given amount of data. The BlockLevelCompression field of DBS Control enables and disables BLC.

BLC can be enabled or disabled system-wide, or for various categories of tables. For Permanent data, these include subtables for primary, fallback, eligible LOB data, and join and hash indexes. Secondary indexes on primary rows and fallback copies of secondary indexes are never compressed.

Related Information

For more information on... See...
BlockLevelCompression field BlockLevelCompression.
COMPRESS and UNCOMPRESS commands Ferret Utility (ferret).
DefaultTableMode field DefaultTableMode
BLOCKCOMPRESSION query band Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144.