If AMPs have been added or dropped since the archive was created, restore cluster and specific AMP archives to all AMPs. Reconfiguration redistributes data among AMPs, therefore rows in the archive do not distribute exactly to the AMPs from which the rows came.
When restoring or copying a No Primary Index (NoPI) table to a destination system that has a different number of AMPs than the source system, there is a high probability that the data will be skewed on the destination system after the restore or copy. This is due to the algorithm that is used by Teradata Database to distribute the data rows onto the AMPs for a NoPI table.
When PPI tables are restored after a change in configuration or platform, it is necessary for the primary index to be re-validated prior to using the table. For all-AMP and multi-stream restores, Teradata ARC automatically attempts to perform this revalidation. If a problem occurs, Teradata ARC displays a warning indicating the cause of the failure and continues the restore job. After the restore job completes, the user must attempt to rerun the revalidate step manually for PPI tables by using either of the following SQL statements:
ALTER TABLE <database>.<table> REVALIDATE; ALTER TABLE <database>.<table> REVALIDATE PRIMARY INDEX;
When Column Partition (CP) tables are restored after a change in configuration or platform, it is also necessary for the table to be revalidated prior to using it. For all AMP and multi-stream restores, Teradata ARC automatically attempts to perform this revalidation. If a problem occurs, Teradata ARC displays a warning indicating the cause of the failure and continues the restore job. After the restore job completes, the user must attempt to rerun the revalidate step manually for CP tables by using the following SQL statement:
ALTER TABLE <database>.<table> REVALIDATE;
Teradata ARC does not automatically revalidate the primary index for dictionary or cluster backups. Additionally, Teradata ARC does not automatically revalidate if the NO BUILD option is specified on the restore, or if RELEASE LOCK is not specified.