Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!XEROX.COM!DKruse.ElSegundo
From: DKruse.ElSegundo@XEROX.COM
Newsgroups: comp.os.vms
Subject: Re: Tape inited wrong
Message-ID: <880122-172759-2254@Xerox>
Date: 22 Jan 88 21:37:10 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 33


>> We have a TK70 tape which was 'init'd under RSTS/E on a PDP-11 (using a
>> TK-50 drive).  The tape now refuses to 'initialize' under VMS, failing with
>> the message "Software write protect"......
>> How do we recover from this one?

> I seem to remember that
> TK50s (and probably TK70s) are formatted at the factory and so bulk
> erasing would destroy the tape (maybe another reader can clear up this
> point).

I discarded the original message on this one since I am not familiar with
TK70's, But I can respond to the case of TK50's.

The TK50 is not preformatted, BUT there are "CALTRACKS" (calibration tracks)
which are written by the drive the first time a new tape is loaded, and never
re-written - even when the tape is "init'd".  That is to say that if these
tracks do not exist the drive assumes a new tape and writes them.  The purpose
of the CALTRACKS is to provide a primary reference point from which the drive
determines the location of the other data tracks independent of the physical
position of the tape, which may change at each load.

Quoting from the TK50 Technical Manual:

"NOTE:
There is no way to rewrite CALTRACKS
except to bulk erase the cartridge,
which destroys all data on the tape."

So, if there is no valuable data on the tape it should be OK to bulk erase it.

I repeat, I am not familiar with TK70's, but this information does apply to
TK50's, and I suspect that they are similar in this case.