the relation of channel with tape drive

[xiazhen]

hi, expert,

    a bit question regards of  the number of  tape drive when nbu backup ,

   i am a confuse it .

    now my situation,    

    when i try to allocate 4 channel . the nbu can only  use a tape drive.  until i addition channel to 8 , the nbu can with second tape drive.

    i lookup file of  rman, it is a channel to a tape drive . why is this ?

   best regards 

[Marianne · Accepted solution]

Look at the MPX setting in the policy schedule and the Storage Unit config.
If both of them are set to 4, then configuring 4 channels will multiplex all of them onto one tape drive.

If you want 1 channel per tape drive, set MPX in policy schedule to 1. Don't change the Storage Unit config - the schedule MPX value will override the STU setting.