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.
- 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.