17.05 - READ Locks and Canceled Rollback Operations - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - SQL Data Manipulation Language

Advanced SQL Engine
Teradata Database
Release Number
Release Date
January 2021
Content Type
Programming Reference
Publication ID
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.