RS/6000 Tape questions

[Warren Jones]

rmilner at zia.aoc.nrao.edu (Ruth Milner) writes:

>We have found the Exabyte tape handling (don't have any other kind) to be ...
>unusual ... compared to the Suns. For example, on a Sun, if you write a file
>onto Exabyte, you can take it away and later on put it back in, skip to the
>end of that file, and write another one. On the RS/6000, not only will it not
>do this at all (I/O error), but if you take a tape with a file written on it 
>by the IBM over to the Sun, the Sun won't write at the end of it any more 
>either! Clearly it's writing something different, but we haven't been able
>to find out what. Anybody have any clues? According to the documentation, 
>they both write a double eof on close, and that doesn't really cause us any
>serious problems.

I think one of the tricks to appending files on the end of a tape is
to _always_ write to the no-rewind-on-close device, e.g. /dev/rmt0.1.
But there seem to be other problems related to tctl.  To put a new
file at the end of the tape, you have to use tctl to skip over the
stuff at the beginning, and "tctl fsf N" doesn't seem to work as advertised.
I've been calling IBM software defect support about this for over
_six_weeks_ now, and still haven't gotten a satisfactory answer.
I'd be glad to hear from anyone else out there who has dealt with this.

Warren Jones
wjones at nwnexus.wa.com