Raising a dynamic exception without previously declaring a user-defined EXCEPTION variable:
SQL>
SQL> BEGIN
2 RAISE_APPLICATION_ERROR(-20001,'A not too original message.');
3 EXCEPTION
4 WHEN others THEN
5 dbms_output.put_line(SQLERRM);
6 END;
7 /
ORA-20001: A not too original message.
PL/SQL procedure successfully completed.