READ Locks and Canceled Rollback Operations - Analytics Database - Teradata Vantage

SQL Data Manipulation Language

Deployment
VantageCloud
VantageCore
Edition
Enterprise
IntelliFlex
VMware
Product
Analytics Database
Teradata Vantage
Release Number
17.20
Published
June 2022
Language
English (United States)
Last Update
2024-04-05
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lifecycle
latest
Product Category
Teradata Vantage™

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.