1. half-opened connections are connections when only one side has responded to connection establisment (three-way handshake)
2. half-closed connections are connections when only one side has responded to connection close request (four-way close).
(see: http://www.scit.wlv.ac.uk/~jphb/comms/tcp.html)
If I got it right, your VPN connection is not being torn down, but the connections inside tunnel get lost. Right? So please provide us with information, what type of database connection it is (I assume TCP) and what time is required to lose database connectivity.
mikrobi,