When you invoke a UDM on a UDT, Teradata Database searches the SYSUDTLIB database for a UDM that has the UDT as its first parameter followed by the same number of parameters as the method invocation.
If several UDMs have the same name, Teradata Database must determine which UDM to invoke. For details on the steps that Teradata Database uses, see Teradata Vantage™ - SQL External Routine Programming, B035-1147.