As soon as you discover that you have lost an online redo log, if the database is still functioning, what should be your first action?
A. Shut down the database
B. Clear the online redo log
C. Back up the database
D. Checkpoint the database
E. Call Oracle support
When you discover that that you have lost an online redo log,and if the database is still up,the first action should be to checkpoint the database.This can serve to reduce the overall risk of data loss.After you checkpoint the database,you can then attempt to clear the online redo log.A backup afterward is highly recommended.
注:在线重做日志丢了就马上checkpoint切换日志
原文：http://www.cnblogs.com/Babylon/p/7805284.html