Which are the correct steps, in order, to deal with the loss of an online redo log if the database has not yet crashed?
A. Issue a checkpoint.
B. Shut down the database.
C. Issue an alter database open command to open the database.
D. Startup mount the database.
E. Issue an alter database clear logfile command.
F. Recover all database datafiles.
A. a, b, c, d
B. b, d, e, c
C. a, b, d, e, c
D. b, f, d, f, c
E. b, d, a, c
If the database has not shut down yet,you have an opportunity to preserve your data changes.Issue a checkpoint,which will flush dirty buffers to disk.Then shut down the database normally,if possible(shutdown,shutdown immediate).You then should mount the database with the startup mount command followed by clearing and rebuilding the log file with the alter database clear logfile command.Finally,attempt to open the database with the alter database open command.
原文：http://www.cnblogs.com/Babylon/p/7805441.html