652.Tape streaming is not happening while performing RMAN tape backup. On investigation, you find that
it is not because of the incremental backup or the empty file backup and that RMAN is sending data
blocks to the tape drive fast enough.
What could be a solution to make tape streaming happen during the backup?
A. Configure backup optimization
B. Configure the channel to increase MAXOPENFILES
C. Configure the channel to increase the capacity with the RATE parameter
D. Configure the channel to adjust the tape buffer size with the BLKSIZE option
Answer: C

RATE Channel Parameter
In the ALLOCATE and CONFIGURE CHANNEL commands, the RATE parameter specifies the bytes per second that are read on a channel. You can use this parameter to set an upper limit for bytes read so that RMAN does not consume excessive disk bandwidth and degrade online performance. Essentially, RATE serves as a backup throttle. For example, if you set RATE 1500K, and if each disk drive delivers 3 megabytes per second, then the channel leaves some disk bandwidth available to the online system.

参考：http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmtunin.htm#BRADV90072