Each table has information about itself stored in a special row called a table header. Table headers are duplicated on all AMPs.
A request for a specific-AMP restore of a table is only allowed on tables without the fallback option. This type of restore is accepted only if a table header for the table already exists on the specified AMP. If a header does not exist, Teradata ARC rejects the request.
When restoring a single processor after a disk failure, use the TABLE REBUILD utility to create the header for the table.
If a header already exists for the table, it must have the same structure as the header on the archive. If the definition of the table is changed without rerunning the archive, Teradata ARC rejects the restore request.
Any data definition statement (for example, ALTER TABLE or DROP INDEX) that is executed for a table also changes the structure (table header) of the table.
If the header structures match, Teradata ARC makes another check for invalid unique secondary indexes for the table. This check ensures that the specific AMP restore does not create a mismatch between data rows and secondary index rows.
If Teradata ARC finds any valid unique secondary indexes, it invalidates them automatically on all AMPs. An all-AMPs restore of such a table invalidates any unique secondary indexes on the table.