Rules that you set to establish and preserve relationships between tables when you add, change, or delete records. Enforcing referential integrity prohibits users from adding records to a joined table for which there is no primary key, changing values in a primary table that would result in orphaned records in a joined table, and deleting records from a primary table when there are matching related records.
If you select the dbRelationDeleteCascade or dbRelationUpdateCascade option for a relationship, the Microsoft Jet database engine allows changes and deletions but changes or deletes related records to make sure the rules are still enforced.