if both are running on VM, I Think the best way is to take a full snapshot.
Please check the following documetation articles explaining this:
You can check online on docs.bmc.com
Its better to take build a new VM and do the upgrade process there with the backup of the DB and configuration files. In case it fails also, you still have the original VM and all the settings.
If your appserver is on a VM, then the snapshot of the VM, snapshot or backup of the file server and then a backup of the database is the way to go. how you take a database backup is up to you but ideally it would be done after you've shutdown the appservers.