I have found thru my most recent of many installations of Veritas Netbackup
and that if you are using the following hardware, you need to follow this;

1. Dell Servers 2300 series or possibly other series Dell Servers
2. ATL P series tape libraries 1000,2000 series TLD's

If you are to utilize both in combination, you need to purchase a 2944UW
controller for the Dell Server to that the ATL tape library can see the Dell
system. The default controller in that server does not work properly and
you will get SCSI parity addressing errors.

Dell Servers and ATL libraries share the SCSI address of 0 and this does
not work well with Dell. So you must configure your ATL library to see other
then SCSI address 0 to start.

If you run into this problem, let me know?