QUESTION 50
The database is running in the ARCHIVELOG mode. It has three redo log groups with one member each. One
of the redo log groups has become corrupted. You have issued the following command during the recovery of
a damaged redo log file:
ALTER DATABASE CLEAR UNARCHIVED LOGFILE GROUP 3;
Which action should you perform immediately after using this command?
A. You should perform a log switch
B. You should make a backup of the database
C. You should switch the database to the NONARCHIVELOG mode
D. You should shut down the database instance and perform a complete database recovery
Answer: B
同628题：http://blog.csdn.net/rlhua/article/details/13280569
Explanation/Reference:
Section: Backup, Recovery & Recovery Manager (RMAN)
SQL> ALTER DATABASE CLEAR LOGFILE UNARCHIVED GROUP 3;
Immediately back up all datafiles in the database with an operating system utility, so that you have abackup
you can use for complete recovery without relying on the cleared log group.
For example, enter:
% cp /disk1/oracle/dbs/*.dbf /disk2/backup
http://www.oracle-dba-online.com/managing_redo_logfiles.htm
This statement clears the corrupted redo logs and avoids archiving them. The cleared redo logs are available
for use even though they were not archived.
If you clear a log file that is needed for recoveryof a backup, then you can no longer recover from that backup.
The database writes a message in the alert log describing the backups from which you cannot recover