17.10 - DisableWAL - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - Database Utilities

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Configuration
Publication ID
B035-1102-171K
Language
English (United States)

Determines whether Write-Ahead Logging (WAL) is enabled.

Field Group

File System

Valid Settings

Setting Description
TRUE The WAL feature is disabled. Changed data blocks and cylinder indexes are written directly to disk. The DisableWALforDBs field is ignored.
FALSE The WAL feature is enabled. The items written to the WAL log are determined by the setting of DisableWALforDBs:
  • If DisableWALforDBs is TRUE, changed data blocks are written to disk, and cylinder index changes are written to the WAL log.
  • If DisableWALforDBs is FALSE, changed data blocks are written to the WAL log and cached in memory, or may be written to disk, depending on the specific operation.

Default

FALSE

Changes Take Effect

After the DBS Control Record has been written.

Usage Notes

WAL is a log-based file system recovery scheme in which modifications to permanent data are written to a log file, the WAL log. The log file contains change records (Redo records) which represent the updates. At key moments, such as transaction commit, the WAL log is forced to disk. In the case of a reset or crash, Redo records can be used to transform the old copy of a permanent data block on disk into the version that existed at the time of the reset.

Data blocks inserted by the MultiLoad utility are always written to disk regardless of the DisableWAL field setting.

Related Information

See DisableWALforDBs.