[evla-sw-discuss] [Fwd: Re: An "In Use" flag for the MIB interface]

[Bill Sahr]

I spoke to Wayne.  He has no objection to posting this email
from him on evla-sw-discuss.   Bill

-------- Original Message --------
Subject: Re: [evla-sw-discuss] An "In Use" flag for the MIB interface
Date: Wed, 16 Aug 2006 10:40:46 -0600
From: Wayne Koski <wkoski at aoc.nrao.edu>
To: bsahr at nrao.edu
References: <44E20CBC.30000 at nrao.edu>

I'm don't like this idea of putting such a flag this low in the M&C
system.  Basically for both the VLBA and VLA the M&C hardware doesn't
decide whether or not to respond to commands they receive, they simply
carry out the task. The decision whether to send the command or not is
made higher up in the system, and I think it should remain that way.

Also, for the VLBA, I can disrupt an observation by sending contrary
commands at any time.  But I check first to see if we are observing,
before I attempt to do anything. So the question I'd like to be answered
is how much time we have lost in observing at the VLBA by someone who
accidentally sent contrary commands.

My final point is that this flag deals with people who accidentally send
a contrary command, but what about a situation were someone needs to
disrupt the observation on purpose?

Here is a made up scenario (hopefully unlikely), but should be something
to consider and to be thought about:

I'm at AW9 working on an antenna.  I see a tornado develop and it is
headed towards AW8 which is observing and the in-use flag is thus set.
I would want (because time is of the essence) to get that antennas ACU
screen up and immediately tell it to stow itself.  With the in-use flag,
I'd have to contact Operations (hopefully no busy signals) to get them
to stow the antenna thus wasting precious time.

Thus, if we want to have an in-use flag, for certain commands, we need
to think about tagging them with an ignore the in-use flag in order to
allow them to still occur.

By the by, the last report for a tornado that I recall was a couple of
years ago, somewhere near the north arm.  Also I've seen antennas with
broken anemometers or their cables.

-wayne-