ON

Specifies that any record with a duplicate index key value not be included in the index file. Only the first record with the original index key value is included in the index file.

OFF

(Default) Specifies that records with duplicate index key values be included in the index file.

An index file retains its SET UNIQUE setting when you issue REINDEX. For more information, see INDEX and REINDEX.

SET UNIQUE is scoped to the current data session.