Oracle Upgrade 10g to 11g

Dear Folks,

I have to do Oracle Upgrade on the following environment:

Environment:

HP UX servers

1 dbCi node and 2 additional app servers on seperate boxes

This is a cluster environment, I have done oracle Upgrades on standalone units but first time on a cluster environment

Any special things that I need to taatrke into consideration or shall I just do the oracle upgrade on the central host and that's it

Help will be appreciated.

Thanks

APS