[Simh] VAX Tape Emulation?

[Clem Cole]

On Thu, Jan 25, 2018 at 4:14 PM, Larry Baker <baker at usgs.gov> wrote:

> Because UNIX tapes and tape drivers cannot write variable-length blocks
> and do not allow skipping forward over records between read operations
>

​That's not a correct statement.   UNIX does it great - I've used it (and
rmt) for years.  UNIX's tape driver is the most flexible of any OS I have
ever used (and I have done tapes on probably greater than 25 different OS's
over the last 40 years).  That's why I suggest it.  I wonder what the issue
for VMS is?

Hmm.. thinking about it, TCP sockets will remove the record orientation
(TCP creates an stream of octets without any records), so if you are doing
the funky RMS like stuff, its TCP that dropping those boundaries not the
UNIX tape driver.   If you want same then it need to be set as meta-data.
But the UNIX tape drive works as expected.   The 'block' size is the size
of the write, although I think the TM11 requires a minimum of 512 bytes.
Records passed with the MTIO ioctl' which mt/rmt all support..

That said,  I agree if he can get DECnet to work, that is likely to better
integrated into the utilities.

Clem

​
ᐧ
ᐧ
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.trailing-edge.com/pipermail/simh/attachments/20180125/b9899fbc/attachment-0001.html>