If you want to avoid problems in an upgrade, you have few changes to make
The first modifications fdepends on your environnement (unix AIX, Solaris, cluster or not). Refer to your install guide ..
By experience, the more important is that there is no activitites on Netbackup environnement : desactivate policies, desactivate Media Servers then stop all services on your Master . You can leave them up because the installation process stops them but I saw several times that they could not be stopped correctly (and the installation aborted)