This is an issue of the network connection completely before the logoff from TSO has completed. You are experiencing the mainframe system's automatic timeout feature, when it will actually log you out of TSO after a certain pre-determined number of minutes of inactivity.
When we originally discovered this issue (that the DAL and SNA*ps 3270 network adapter does not log a user completely out of TSO after the DAL Server session is terminated by the DAL CLient), the only workaround seemed to be to log on to TSO and reconnect, which would then actually complete the "logoff".
However, now we have a better solution. The issue seems to be that the DAL Client is getting out of the SNA*ps network connection a bit too quickly.
Fortunately, the solution is simple. At the end of the logout sequence of the DAL connection script, add a match for something unique on the VTAM Splash Screen. This will cause the network connection to remain open until the exit from TSO has been completed all the way through to the VTAM Splash Screen.
This results in a clean logoff from TSO which will allow subsequent DAL TSO connections without failures, such as the "user is already connected" TSO error message.
A sample logout sequence would look like:
:\\mREADY\\w1\\slogoff\\r\\mLogon:
rather than:
:\\mREADY\\w1\\slogoff\\r: