CompressPermPrimaryDBs
Purpose
Specifies conditions under which data blocks (DBs) for permanent data in primary data subtables will be compressed by default.
Note: Compression is subject to the “BlockLevelCompression” setting, and to the criteria specified by the “MinPercentCompReduction” and “MinDBSectsToCompress” DBS Control settings. DBs not meeting these minimum criteria will not be compressed.
Field Group
Compression
Valid Settings
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Setting |
Description |
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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. |
Default
ONLYIFQBYES
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 Database 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, only primary, fallback, and CLOB subtables, and join and hash indexes are eligible for BLC. Secondary indexes on primary rows are never compressed, but fallback copies of secondary indexes can be compressed to save space.
Related Topics
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For more information on... |
See... |
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BlockLevelCompression setting |
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COMPRESS and UNCOMPRESS commands |
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BLOCKCOMPRESSION query band |
SQL Data Definition Language. |