16.20 - Referential Integrity Revalidation on LOB Tables - Teradata Vantage NewSQL Engine

Teradata Vantageā„¢ NewSQL Engine Node Software Migration Guide

Teradata Database
Teradata Vantage NewSQL Engine
March 2019

Referential integrity is the term used to define the keys and checks that ensure that related values and indexes can be maintained between tables within the database. These relationships are also known as foreign key references. Referential integrity is a connection between multiple tables such that changes to one table cause changes in the other table.

After a migration where data rows may have been redistributed to different AMPs, the Referential Indexes (RIs) must be revalidated before the tables with referential integrity can be accessed. Establishment of a foreign key reference creates a Referential Integrity error table. Because of the way table names are constructed, any data rows in the RI error table contain information that is valid only on that system. If the RI error table is migrated to a different system, any attempt to revalidate referential integrity on the new system fails. If an RI error table is migrated to a different system, the table should be emptied.

Referential integrity on LOB tables should be dropped prior to archival, or referential integrity cannot be reestablished after migration. The rehashlobs.pl script would fail because it cannot drop the rows on the original table involved in a reference.