If you update relationship details in the custom columns of a relationship base object record, the MDM Hub updates the cross-reference record associated with the relationship record.

If you update relationship details in the system columns of a relationship base object record, the MDM Hub inserts new record versions to the associated cross-reference table. System columns are columns such as Relationship Type, Hierarchy Type, Period Start Date, and Period End Date. Also, if you update a relationship from a source system that does not have a corresponding cross-reference record, the MDM Hub adds a new record version to the cross-reference table.