I think if you write anything at the beginning of a DLT tape then all
previously written information will be unreadable and for practical
purposes will have been deleted.  I know that 8mm tapes behave in this
way, and I think DLTs do also.  

If DLTs have this behavior then it will remove any label which exists
on the tape.

Here are two methods which might work.  Make sure the tape is rewound
before trying either of these.  Also be certain that you don't want
any data on the tape.  I suspect that it will be nearly impossible to
recover anything that was on the tapes after you run either of these
commands.

mt -f /dev/rmt/0 weof

The above command should write an end of file mark onto the tape.

dd if=/dev/zero of=/dev/rmt/0 bs=1k count=1

The dd command above will write 1k of zeros onto the tape.

Good Luck.

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Jonathan Meyer
(781)398-6594
UNIX Systems Administrator
Paramtric Technology Corporation
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