OK, now is question, how can I recognize hanging client session? (There is
about 150 sessions at the time)

I did "q sess" to file last time it happens, but all session were at "Run"
state. In addition ... when I recognize it and cancel it, will the client
reestablish session with server to end up backup?

I see no good solution for this situation in automated manner (this is what
I need), except of prevent it - this means write script to test if no client
sessions are started at the time, disable clients, start expiration, and
past it stops, enable clients.
Any other idea?

Tom