Dictionary Cache | SQL Request and Transaction Processing | Vantage - 17.10 - Dictionary Cache - Advanced SQL Engine - Teradata Database

Teradata Vantageā„¢ - SQL Request and Transaction Processing

Product
Advanced SQL Engine
Teradata Database
Release Number
17.10
Release Date
July 2021
Content Type
Programming Reference
User Guide
Publication ID
B035-1142-171K
Language
English (United States)

The Dictionary Cache

The dictionary cache is a buffer that stores the non-demographic Data Dictionary information most recently used to process SQL queries. The database caches the most recently used statistics and demographic data in the statistics cache (see Statistics Cache).

Vantage uses information from the Data Dictionary about privileges, tables, columns, views, macros, triggers, stored procedures, and other objects to transform an SQL request into the AMP steps needed to process a request. For information about AMP steps, see OptApply.

Caching Data Dictionary information reduces the I/O operations required to perform the following actions:
  • Resolve database object names
  • Validate object and row-level security privileges

If an SQL request modifies the contents of the Data Dictionary, the database sends a spoil message to every PE on the system, directing them to drop the modified definitions from their respective dictionary caches.

The database purges the dictionary cache periodically, one PE at a time.

For the current default and maximum sizes of the dictionary cache, see the documentation for the DBS Control field DictionaryCacheSize in Teradata Vantageā„¢ - Database Utilities, B035-1102.