Thanks to Jan Mark Holzer for walking me through this.
I had an old entry left from the former tape drive.
# hwmgr -show scsi
42: 1 bicoid tape none 0 1 (null)
46: 5 bicoid tape none 0 1 tape1 [0/6/0]
I first had to remove the null entry
# hwmgr -delete comp -id 42
hwmgr: Delete operation was successful
before moving tape1 to tape0
# dsfmgr -m tape1 tape0
tape1=>tape0 tape1_d0=>tape0_d0.....
if that didn't work Jan suggested the following:
> If this doesn't help you can check your /etc/dfs*.dat files for
> an old tape entry and take the HWID from this entry and use
> dsfmgr to delete this entry using dsfmgr -R hwid
> #HWIDoftheEntry.
>
> The HWID is in the 4th column of the /etc/dfs*.dat
>
> Ie.
>
> # hwmgr -v d | grep tape
> 121: /dev/ntape/tape1 DEC TZ89 (C) DEC
> bus-1-targ-2-lun-0
>
> # dsfmgr -m tape1 tape0
> dsfmgr: ERROR: second device status is active: tape0
>
> # grep 'tape 0' /etc/dfsc.dat
> A: 0 13001b4 96 34 18 c ""
> /dev/ntape/ tape 0 ""
>
> # dsfmgr -R hwid 96
> [...Output delted...]
> # dsfmgr -m tape1 tape0
Received on Mon Sep 02 2002 - 13:53:25 NZST