Selecting the SSH Tunnel option will automatically spawn a SSH tunnel process that
the current connection will use. The tunnel process can be shared if two connections use the same port.
This is useful when you are using a SSH server as a relay to another host. (A <-->B<-->C).
The SQL keep alive option is for use in a relay situation (A <-->B<-->C)
By default the SSH tunnel will automatically send keep a alive between A and B, but not between B and C.
When checked, the SQL keep alive will issue a query to the pg_database system table with a limit of one row set.
This will keep the connection alive from A to C.
A connection that is connected via a SSH tunnel will have a red screen: 