Netbackup/Vault 4.5 running on 5.6 Solaris server with STK silo with 2 9840
tape drives.

  I have vault 4.5 running which takes up both my drives when vault is
running.  I have an important Database backup that must be performed to
backup the arch files.  If this backup doesn't get done the DB can't write
its arch files and the DB will go down.  This arch backup is started from
the client whenever the arch directory hits a certain threshold so the time
this backup starts in not set at a given time; it could be several times a
day at any given hour.  
   I only have 2 drives and when vault is running 1 drive is reading and the
other drive is writing.

  Question
      With the set up described above, if my vault backup is running and
will take a couple of hours, but I have this DB arch backup that suddenly
wants to try to run, will it interrupt vault when its busy switching between
"read" tapes?  If no, how can I have an important backup run while vault is
running and I only have 2 drives?  Does vault use priorities like backups
do?  What can I do?

Thank You
David