The iSeries will send a keep alive probe to the client depending on the Change TCP Attributes (CHGTCPA) TCPKEEPALV value.
The sonic firewall my block this thus causing the session to drop. Best way to fix this depends on the TN5250 client you are using. See if they have a keep alive setting and set it to be less then the value on your iSeries.
Director of Information Services
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Mike Krebs
Sent: Thursday, March 13, 2014 1:02 PM
To: Midrange Systems Technical Discussion
Subject: Re: Sonic Wall and Sessions Dropping
I can confirm we had the same problem when testing our DR plan (uses SonicWall). Our DR vendor fixed and I don't know what it was exactly. There is some kind of timeout. If you use the PC client, do the sessions drop like they do through the tunnel?