If you attempt to add or drop a method signature from the specified UDT, the system aborts the request if any cast, ordering, or transform set definition in the system references the method (see CREATE CAST and REPLACE CAST, CREATE ORDERING and REPLACE ORDERING, and CREATE TRANSFORM and REPLACE TRANSFORM).
This action protects the integrity of the database from corruption caused by objects depending on the previous definition of a structured UDT that is no longer correct.