怎样在Oracle 10g存储过程中log错误行

CREATE OR REPLACE PROCEDURE top_logging IS  demo number;begin  select * into demo from dual;EXCEPTION  WHEN OTHERS THEN    dbms_output.put_line(dbms_utility.format_error_backtrace());END top_logging;/ SQL> exec TOP_LOGGING;ORA-06512: 在 "SYS.TOP_LOGGING", line 4