Re: 3270 session disconnects

Rob,

Are these disconnects simply session drops where you can log back on
with some kind of "reconnect" option (like TSO has) and get right back
to where you were? Do you lose your VTAM LU? To what degree are you
disconnected?

If you can reconnect and get your old session back unmolested, the
problem might be network.

If you cannot reconnect and get your old session, and you end up having
to reconnect to a new LU because the old one has been released by VTAM,
then maybe it's an application timeout or session management software
timeout of some kind (or an application issue).

If you're getting a full VTAM drop, look for the IST messages that come
out at that time, and go read the sense code information in the SNA
Sense Codes table, and see where that leads you.

If all else fails, you can start a GTF for your own LU under VTAM, and
inspect what you get from that when the disconnect occurs. Maybe one or
more GTFs will reveal what application or layer of software is signaling
the end of session. If you get a specific abend, you might be able to
get a good SLIP trap put in for that too, but that's more of a long shot
compared to a blanket GTF for an "unknown" problem.

If you suspect the network, get one of your net guru's to put a sniffer
on your IP address between you and the frame, and see what it captures
at the time of failure - maybe there is a failing network component.

These kinds of problems range from simple (application timeout value,
seen that & easy fix), to thorny (dumb network cable for frame ran under
the DASD array, and at a busy time there was enough EM interference from
busy disk drives to cause occasional link failure - seen that and it
drove us nuts trying to figure it out -- moved cable & all good).

Best of luck to you and hope this helps,

Gary Diehl
Systems Administration
"One machine can do the work of fifty ordinary people. No machine can do
the work of one extraordinary person." -Elbert Hubbard

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