When you say ‘update’ can you further define what you mean? Are you just doing an inplace upgrade of ARS and Mid Tier? Do you have applications? is it in a server group? Are you on Windows w/MSSql or Oracle or Linux? What new features are you looking for?
the guide for upgrading is here: Planning an upgrade - Documentation for BMC Remedy ITSM Deployment 9.1 - BMC Documentation
if you need planning assistance, please contact me.