SELECT * FROM DBA_PROFILES WHERE RESOURCE_NAME='PASSWORD_VERIFY_FUNCTION';

ALTER PROFILE &PROFILE. LIMIT PASSWORD_VERIFY_FUNCTION &function_name.;

CREATE OR REPLACE FUNCTION dummy_func
 (USERNAME VARCHAR2, PASSWORD VARCHAR2, OLD_PASSWORD VARCHAR2)
 RETURN BOOLEAN IS
 BEGIN
   IF NLS_LOWER(password) = NLS_LOWER(username) THEN
      raise_application_error(-20001, 'Password is the same as the username');
   END IF;
   RETURN(TRUE);
END;