This is actually a function of the SNA Server setup.
When an SNA Server connection is defined in Screensurfer,
you simply give the name of the SNA Server "pool" you will
be connecting to.
It actually is the SNA Server Client component executing on
the Screensurfer server that determines where to obtain and
LU session from the named pool.
While I have understood that it is possible to setup
failover within an SNA Server cluster, I don't know how to
In Screensurfer itself, you can use the *ANY connection
type, try to connect to one pool name and if it's down, try
the next, but I think that the native SNA Server support
for failover would be a better approach.