Rules for Order Mapping UDFs
If you specify a UDF as the MAP routine for an ordering, it must obey the following
It must have one and only one parameter.
The data type of the single parameter you specify must be the same as that of the
UDT specified as UDT_name.
The result data type must be a predefined data type.
Its predefined data type is valid except the following:
It must be declared to be DETERMINISTIC.
The name you specify for it in the ordering definition must be the name of a UDF contained
within the SYSUDTLIB database.
See “CREATE FUNCTION (External Form)/ REPLACE FUNCTION (External Form)” on page 240 for details about UDF parameters, result data types, and the DETERMINISTIC option.