17.05 - READ Locks and Canceled Rollback Operations - 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)

When you use the RcvManager utility to cancel a transaction rollback, the system marks the base table on which the rollback was canceled as nonvalid. As a result, the table cannot be updated. With some restrictions, you can inspect the rows of the nonvalid base table if you specify a LOCKING FOR READ OVERRIDE modifier.

The following rules document the restrictions on the use of a LOCKING FOR READ OVERRIDE modifier:
  • You can only read from a single base table using this modifier. Attempts to perform multitable operations return an error.
  • You can specify LOCKING FOR READ OVERRIDE for any single base table, whether a rollback has been canceled on that table or not.
  • The Optimizer only uses indexes to read base valid base tables. If you use LOCKING FOR READ OVERRIDE to access a nonvalid table, then the system always uses a full-table scan.