One not-to-be ignored benefit of using exp/imp as well as RMAN backup/restore is that if you (or more likely, someone else in the DBA/sysadmin team in the future) manage to mess up one backup method, you still have the other one as a long-stop. Of course only you/your site can compare the value of the reduction of risk you run vs the additional cost of maintaining two backup systems. Regards Nigel