This is a desk DMX backup scenario / issue
If you want a server as a backup without DMX - then you have to record all your cues as Presets and put them in a cuelist within catalyst...
However, the easiest way is to get a backup HogIII and network the DP's so that you have redundancy
Its a bit much to expect a catalyst server to perform as a backup for another bit of equipment that may fail (ie your hogIII)...
S