15.00 - DefaultTableMode - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
15.00
Content Type
Configuration
Publication ID
B035-1102-015K
Language
English (United States)
Last Update
2018-09-25

DefaultTableMode

Purpose  

Determines how BLC is managed for Permanent storage tables that have the BLOCKCOMPRESSION option set to DEFAULT, or that do not have the BLOCKCOMPRESSION option explicitly specified when the table is created.

Field Group

Compression

Valid Settings

 

Setting

Description

MANUAL

BLC is applied based on the settings of these DBS Control fields: “CompressPermPrimaryDBs”, “CompressPermFallbackDBs”, “CompressPermPrimaryCLOBDBs”, “CompressPermFallbackCLOBDBs” which determine the default BLC for these table types at the time the table is created. These defaults can be overridden using the BLOCKCOMPRESSION query band at load time.

Tables can be compressed or uncompressed at any time after loading by using the Ferret COMPRESS and UNCOMPRESS commands.

Data inserted into existing tables inherits the current compression status of the table at the time the data is inserted.

AUTOTEMP

BLC is automatically performed by Teradata Database based on the frequency of access to the table data (the data temperature). Temperature-based BLC (TBBLC) compresses infrequently accessed data, and uncompresses data that it is accessed frequently.

Note: If temperature-based BLC (TBBLC) is disabled, tables that are set to use AUTOTEMP will behave like tables set to use MANUAL compression until TBBLC is enabled again. TBBLC is enabled and disabled using the “EnableTempBLC” setting.

NEVER

Data in the table is never compressed at the data block level.

Default

MANUAL

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.

Data temperature refers to the frequency of access. Hot data is frequently accessed. Cold data is infrequently accessed. Warm data is accessed moderately frequently. TBBLC automatically compresses colder data to save storage space, and decompresses the data if it becomes hotter. At any time, different portions of a table, such as different partitions, may exist in different states of compression depending on their temperatures.

Related Topics

 

For more information on…

See…

Block-level compression

“BlockLevelCompression” on page 241 and Database Administration.

BLOCKCOMPRESSION table attribute

SQL Data Definition Language.

EnableTempBLC setting

“EnableTempBLC” on page 328.

Ferret COMPRESS, UNCOMPRESS, and FORCE commands

Chapter 13: “Ferret Utility (ferret).”

Query bands for compression

SQL Data Definition Language.

Storage group of DBS Control settings

“Storage Group” on page 484.