Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!ames!lll-winken!uunet!psgdc!rg
From: rg@psgdc (Dick Gill)
Newsgroups: comp.unix.questions
Subject: Re: Need HELP recovering files from tar damage
Keywords: tar corrupt file
Message-ID: <230@psgdc>
Date: 17 Jul 89 22:03:44 GMT
References: <4385@merlin.usc.edu> <18567@mimsy.UUCP> <11668@orstcs.CS.ORST.EDU> <970@mplvax.EDU>
Reply-To: rg@psgdc.UUCP (Dick Gill)
Organization: Professional Solutions Group, Vienna VA
Lines: 34

In article <970@mplvax.EDU> cdl@mplvax.ucsd.edu.UUCP (Carl Lowenstein) writes:
>In article <11668@orstcs.CS.ORST.EDU> pvo@oce.orst.edu (Paul V O'Neill) writes:
>
>>Keep in mind that if you made the c/x error while at BOT, or anywhere on
>>track 1 of a QIC tape, that the drive turned on it's FULL WIDTH erase head
>>as it was writing to track 1 and also wiped anything you had further on
>>down the line in tracks 2 - 9.
>
>Do these QIC cartridges not have some kind of mechanical write lock that
>signals to the drive electronics? 
...

They sure do, at least the 3M-DCxxx series cartridges used on
NCR Towers, IBM RT's, Fortunes and, I suspect, many other unix
machines.  Looking at the upper left corner of the cartridge
(with the tape at the top) you will see a circular plastic piece
with  a slot in it and an arrow on it. To the right will be the
word 'safe'.  If you turn the circular plastic piece so that the
arrow points to the word 'safe', tape drives will not be able to
write on the cartridge.

When we have clients who REALLY need the data on a backup tape
(disc crash, major upgrade, etc.), the first thing we instruct
them to do is to turn the arrow to SAFE on the backup casettes.
It takes no time, and offers protection against the unfortunate
slip of the finger which can wipe out your safety net in a
second.




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Dick Gill     Professional Solutions Group   (703)761-1163   ..uunet!psgdc!rg