En absoluto, no existe tal limitación para ningún tipo en los argumentos, hago un copy/paste de la documentación, Referencia SQL, CREATE PROCEDURE.
datatype
Specify the datatype of the argument. An argument can have any datatype supported by PL/SQL.
Datatypes cannot specify length, precision, or scale. For example, VARCHAR2(10) is not valid, but VARCHAR2 is valid.
Oracle Database derives the length, precision, and scale of an argument from the environment from which the procedure is called.
http://download.oracle.com/docs/cd/B...htm#SQLRF01309
Saludos