053-134

You are managing an Oracle Database 11g database. You want to take a backup on tape drives of the USERS tablespace that has a single data file of 900 MB. You have tape drives of 300 MB each. To accomplish the backup, you issued the following RMAN command:
RMAN>BACKUP
SECTION SIZE 300M
TABLESPACE users;
What configuration should be effected to accomplish faster and optimized backups by using the above command?
A. The SBT channel must be configured, with the default parallelism setting for the SBT device set to 1.
B. The COMPATIBLE initialization parameter for the database instance must be set to at least 10.0.
C. The SBT channel must be configured, with the parallelism setting for the SBT device set to 3.
D. The SBT channel must be configured, with the MAXPIECESIZE set to 300 MB.

SBT(system backup to tape)
相关题 146
没机会验证但是从官方答案对的假设出发来验证正确答案和错误答案，C为什么错？
       磁带机(tape drive)有性能瓶颈，多通道没必要，RAID本身已经是并行处理。
　　磁带机只能有一个全高或半高驱动器，磁带机型号不同，驱动器类型也不相同，由于驱动器数量的限制磁带机一次只能执行一个备份任务。而磁带库则可以根据不同型号规格选配一个或多个FC,SAS或SCSI驱动器（TS2900除外，TS2900只能有一个SAS驱动器），因此可以一次执行多个备份任务。
　　磁带机是单机,它的容量就是磁带的单盘容量,它的最大传输速率即该磁带机技术的传输速率。
最后只能归结到多通道并不能让磁带机更高效。