17.05 - Locks and Concurrency - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Manipulation Language

Product
Advanced SQL Engine
Teradata Database
Release Number
17.05
Release Date
January 2021
Content Type
Programming Reference
Publication ID
B035-1146-175K
Language
English (United States)

A DELETE statement sets a WRITE lock for the table, partitions, or row. For a nonconcurrent load isolated delete operation on a load isolated table, the delete operation sets an EXCLUSIVE lock.

For a SELECT subquery, the lock depends on the isolation level for the session, the setting of the AccessLockForUncomRead DBS Control field, and whether the subquery is embedded within a SELECT or DELETE statement.

Transaction Isolation Level DBS Control AccessLockForUncomRead Field Setting Default Locking Severity for Outer SELECT and Ordinary SELECT Subquery Operations Default Locking Severity for SELECT Operations Embedded Within an UPDATE Request
SERIALIZABLE FALSE READ READ
TRUE READ
READ UNCOMMITTED FALSE READ
TRUE ACCESS
For more information, see:
  • SET SESSION CHARACTERISTICS AS TRANSACTION ISOLATION LEVEL in Teradata Vantage™ - SQL Data Definition Language Detailed Topics , B035-1184
  • Teradata Vantage™ - SQL Request and Transaction Processing, B035-1142
  • Teradata Vantage™ - Database Utilities , B035-1102