Re: OPA0 Console connection

On Tue, 14 Mar 2006 00:10:22 GMT, Hoff Hoffman <hoff@xxxxxxxxx> wrote:

In article <ops6diokhnzgicya@hyrrokkin>, "Tom Linden" <tom@xxxxxxxxxx> writes:
:Let me summarize what I have undercovered so far.
:
:firstly the COM1 port seems to be named TTA0 and the COM2 OPA0.
:Why not just call them COM1 and COM2?

Well, you can call them anything you want, of course. OpenVMS
has always called the console port OPA0:, meaning -- if we changed
it -- we'd tend to bust stuff. (And we tend not to like to do
that when we can avoid it.)

Even more interesting, COM1 and COM2 don't always map the same
way, as these can be an OP device or a TT device based on the
system firmware configuration.

Just to make sure I understand, of the two ports (in this case) one being TTA0
and the other OPA0, do I have to be on OPA0 to speak to SRM or can I also
do it from TTA0?

:If you need to use the other names, make them an alias.

What's an "alias", in this context?

If I wanted other names for a device, then I would tend to define
site-specific logical names for the constructs -- but to define
these tends to cause as many problems as it solves, as we learned
back in MicroVAX days. (Do see the MICROVAX subroutine within
SYLOGICALS.TEMPLATE.) We still define these old logical names,
as there is stuff around that still uses them -- but the names
don't scale particularly well, and users and programmers then
eventually tend to use logical names or such to implement the
required mapping for the particular application requirements.

Things are really getting interesting with devices and device
naming and such, but that's fodder for another discussion --
and maybe one at the bootcamp.

Well it would be nice to have names like $9$dvd instead of $9$DQA0:
or $9$floppy instead of $9$DVA0:

:Secondly, suggested remedy in the FAQ, in fact
:disables login from that port, so that is not the right approach.

It is the correct approach. You have to disable the typahead to avoid
the bouncing logins, and you need to enable it to get the login -- and
having two ports back-to-back means you have to choose which one is the
one that will originate, and which will receive the connection.

So how to leave a console cable attached without crashing the system is
:still not solved. BTW if I leave it attached to a W2K problem does not
:occur.

You just haven't seen the problem yet. Anything that can or does
generate a framing error on the line will trigger the halt.
OK, I understand, you can't leave it attached too long, and how long is that?

My preference here is a terminal server, as it does what you want,
and you can (relatively) secure it against unauthorized access,
and you don't need to worry about which end of the connection is
the initiating and which is the receiving. (The terminal server
always initiates the connection to the console, meaning you don't
have to worry about folks connecting into it.)
That would be my preference too, and ebay willing, it may happen:-)


---------------------------- #include <rtfaq.h> -----------------------------
For additional, please see the OpenVMS FAQ -- www.hp.com/go/openvms/faq
--------------------------- pure personal opinion ---------------------------
Hoff (Stephen) Hoffman OpenVMS Engineering hoff[\0100]hp.com


.

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