I realize this is a very old post. I am also experiencing the same issue under 12.10.0.30 while either using VPN or working onsite.
At first connect I have the schema browser and editor window opened. This generates 2 sessions as see by the DBA.
When in it for about 8 mins I am disconnected with the end of communication error from oracle. The DBA is still seeing 2 active connections. My editor window is no longer connected. Meanwhile the schema browser is still connected and operational.
This is not a timeout issue, the timeout is set for 30 mins.
At this point I can open another editor window without reconnecting and work as if I have never been disconnected. At this point the DBA now sees 3 sessions. I am still unable to use the initial editor window while the other two are fine.
There is nothing on the DB side to indicate oracle disconnected the editor session. It seems to be a TOAD bug.
I have opened a SQLPlus window and was able to have it sit idle for 25 mins with no problem whatsoever.
At this point I can open another editor window without reconnecting and work as if I have never been disconnected
Toad would silently reconnect your session in many cases, but not in all. The intended behavior after a dropped session is to disallow automatic reconnect for security. This is improved in 13.1 so that a dropped session remains in a disconnected state until you explicitly re-establish it. If you have password saving enabled you can just click the Test Connections button and Toad will reconnect. Users that have disabled password saving will need to resupply passwords. Toad 13.1 is in beta now and is to be released in the Fall.