OverrideARCBLC - Advanced SQL Engine - Teradata Database

Database Utilities
Product
Advanced SQL Engine
Teradata Database
Release Number
17.00
Published
June 2020
Language
English (United States)
Last Update
2020-06-15
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dita:id
B035-1102
lifecycle
previous
Product Category
Teradata Vantage™

Purpose

Determines whether database tables restored from archives are block-level compressed according to the effective BLOCKCOMPRESSION setting of each table at the time of archiving or according the system-level BLC defaults at the time the tables are restored.
This field does not affect tables with effective BLOCKCOMPRESSION values of ALWAYS or NEVER.

Field Group

Compression

Valid Settings

Setting Description
TRUE The system default settings for block-level compression are used to determine whether restored tables are block-level compressed.
FALSE The effective table BLOCKCOMPRESSION value at the time of archiving determines whether restored tables are block-level compressed.

Default

FALSE

Changes Take Effect

After the DBS Control Record has been written.

Usage Notes

This field does not affect tables with effective BLOCKCOMPRESSION values of ALWAYS or NEVER. This includes tables that were created or altered to have their BLOCKCOMPRESSION option:
  • set to ALWAYS or NEVER
  • set to DEFAULT, and the DefaultTableMode DBS Control field is set to ALWAYS or NEVER
  • unspecified, and the DefaultTableMode DBS Control field is set to ALWAYS or NEVER

This field does not affect subtables for which the effective BLOCKCOMPRESSION is set to ALWAYS or NEVER on the target system to which the data is restored.

For permanent tables and global temporary tables, different subtables hold primary data, fallback data, and LOB data. BLC for these categories of data can be independently controlled using DBS Control Compression fields 14 - 21 (Compress...DBs fields). These subtable settings are effective only when the BLOCKCOMPRESSION setting for the corresponding base table is set to MANUAL, either explicitly, or as a result of being set to DEFAULT (or left unset) while the DefaultTableMode DBS Control field is set to MANUAL.

Block compression that is controlled by the BLOCKCOMPRESSION query band takes precedence over the OverrideARCBLC field setting.

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.

Related Topics

For More Information on… See…
Block-level compression Teradata Vantage™ - Database Design, B035-1094
DBS Control fields that determine effective BLOCKCOMPRESSION value for different types of subtable data
BlockLevelCompression field BlockLevelCompression.
BLOCKCOMPRESSION table option and BLOCKCOMPRESSION query band Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144