I have read the primus article on changing the host failover mode.  The server is a HP-UX server am I correct in thinking that as long as the volumes are not presented ( vgexport) and there is no I/O I can change the failover mode whilst the server is running but it will then need a reboot to apply the new failover changes?

or does the server have to be down then apply the change and restart the server

What is the safest and best way of applying the change