You execute the following command to perform a backup by using Recovery Manager （RMAN）： RMAN> run 
{allocate channel c1 type sbt; 
backup datafile 1; 
} 
The command errors out. A part of the error message is as follows： 
RMAN­03009： failure of allocate command on c1 channel 
ORA­19554： error allocating device， device type： SBT_TAPE， device name： 
What could explain why the statement failed？（）

单项选择题You observe that the senior database administrator always uses the following command when connecting to Recovery Manager （RMAN）， and then starts executing commands to backup the database files：  $ rman target    What would be the effect of this command？（）

A.RMAN would use the current operating system location to place the backup.
B.RMAN would use the control file of the target database to maintain the backup.
C.RMAN would use the recovery catalog of the target database to maintain the backup.
D.RMAN would use the control file of the target database to maintain the backup metadata. 
E.RMAN would use the recovery catalog of the target database to maintain the backup metadata.

单项选择题In Recovery Manager （RMAN）， you set the retention policy to NONE by executing the following command：  CONFIGURE RETENTION POLICY TO NONE  What would be the impact of this setting？（）

A.The retention policy is cleared.
B.RMAN does not consider any backup as obsolete.
C.The retention policy is set to its default setting of redundancy 1.
D.The retention policy is set to its default setting of recovery window 7.

多项选择题In Recovery Manager （RMAN）， you have set control file autobackup to ON by using the following command：  CONFIGURE CONTROLFILE AUTOBACKUP ON  Which two events would cause the control file to be backed up automatically？ （）

A.a tablespace is taken offline
B.the database instance is restarted
C.a new data file is added to an existing tablespace
D.a successful backup is recorded in the RMAN repository
E.the RMAN connection is disconnected from the target database

单项选择题You set the recovery window to seven days and the backup optimization to ON using the CONFIGURE command of Recovery Manager （RMAN）. The most recent backup of the TOOLS tablespace to disk was taken on January 3. The TOOLS tablespace is read­only.  On February 21， when you execute a command to back up all the tablespaces to disk， you find that RMAN backs up the TOOLS tablespace also， even though the contents of the tablespace have not changed after the backup on January 3.  Because there are no changes made to the TOOLS tablespace， you decide that the tablespace should not be backed up by RMAN. What can you to do skip backing up the TOOLS tablespace without changing the current backup optimization setting？（）

A.configure a default device for RMAN backups
B.temporarily disable the retention policy for RMAN backups
C.configure automatic channel allocation for RMAN backups
D.use the CONFIGURE command to reconfigure the recovery window to 60 days

单项选择题You defined the Recovery Manager （RMAN） retention policy to recovery window of 7 days by executing the following command：  RMAN> CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 7 DAYS  When a backup is performed， what would be the status of this backup after seven days？（）

A.The backup would be marked as invalid.
B.The backup would be marked as obsolete.
C.The backup would be removed from the media.
D.The backup would be removed from the RMAN repository.