To perform a CREATE CAST statement, a user-defined cast that performs the same conversion cannot exist or the statement returns an error to the requestor.
|IF you perform a REPLACE CAST statement and there is …||THEN the system …|
|no existing user-defined cast that performs the specified conversion||creates a new user-defined cast.
The result is the same as if you had performed a CREATE CAST statement with all the same specifications.
|an existing user-defined cast that performs the specified conversion||replaces the existing user-defined cast definition with the newly defined cast routine.|
If the cast routine is a method, then that method must be already be defined or the system returns an error to the requestor and does not register the method for casting.