Here in BT Business we have what we call 'primary' and 'secondary' users of our system.
The primary user is, as you might have guessed, in overall control: the primary user can do more things than a secondary user, like reset passwords, add new users, and so on. There is only one primary user.
There can be more than one secondary user. The primary user gives secondary users access to particular parts of the system and lets them do specific tasks only.
If you're upgrading and have tasks to complete, you'll need to sign in as the primary user.