Example (Oracle):

DECLARE
    SUBTYPE fff IS BINARY_INTEGER;
    SUBTYPE ggg IS NATURAL;
    PROCEDURE foo (a IN ggg) IS BEGIN NULL; END;
    PROCEDURE foo (a IN fff) IS BEGIN NULL; END;
BEGIN
    NULL;
END;

You cannot overload subprograms which parameters differ only in subtypes. For example, you cannot overload procedures where one accepts a BINARY INTEGER parameter and the other accepts a NATURAL parameter. For more information about restrictions on procedure overloading, see Restrictions on Overloading at docs.oracle.com.