[comp.sys.hp] Going Past Physical End-of-Tape

ray@vantage.UUCP (Ray Liere) (03/08/89)

We have an HP9000/540 with an HP7970E tape drive, running HP-UX 5.21.

I am having trouble getting the system to know when it has reached the
iphysical end of the tape -- i.e, the foil strip.

This all started by my wanting to mount a tape, go all the way to the
end, and then rewind it. I had heard that this was a good idea on new
tapes, and also for ones that have had information archived on them
for a while -- to relieve any interlayer tape stress and to also
juggle/jiggle/jumble the tape layers and thereby reduce print through.

So, I figured ... easy! I wrote a script that issues "mt fsf" repeatedly,
figuring that when it gets to the foil, mt will generate an error, I will
detect the error and rewind the tape.

Here are our /dev/rmt entires --
crw-------   1 root     other     11 0x040004 Jul 15  1985 0mn
crw-------   1 root     other     11 0x040006 Mar 27  1985 0mn.bcm
(the second one is Berkeley Compatibility Mode -- whatever that is ...
needed per the mt command's documentation)

I tried both /dev's, with the same result: the tape goes past the foil
and off of its reel!

I read in the System Admin manual about a compatibility bit dealing
with tape driver changes made between 4.2 and 5.x, to allow some of the newer
tape drives to stream. Also there is mention of this change in the update
documentation that comes (in a file) with HP-UX updates.

There is a difference of opinion in which bit you flip (0x000008 or 0x000080),
depending on where you read ... so I tried both and still no luck.

It would seem to me that detecting EOT would be super important when you are
writing or reading a tape. We use mainly cartridge tapes, so perhaps I have
been lucky so far and never written/read a full reel of tape -- surely the
system allows one to (easily) detect EOT ... or do I have to be writing/
reading (rather than skipping?).

Thanks for any enlightenment that you can provide.


Ray Liere
Vantage Consulting and Research Corporation
voice: (503)657-7294
uucp: hplabs!hpfcla!hpubvwa!vantage!ray