This is much more complicated than what it seems. If you are not careful, you may end up doing a floor by floor audit.
If you need to work on the management server or information server, you might want to export the list of current users, online and offline. This is especially critical if you are doing major version upgrades or moving clients to new servers.
After the works, compare with the users shown in the server and the exported list. Manually cross-check for if the users still exist. Missing users if any should be rectified immediately. If you have stringent endpoint security in place, these users will lose their network connectivity when the patterns go out of date.
Thereafter monitor the status for successful deployment of pattern and engine updates to all users.
Now you can see the importance of having the original list of users. If you have not done it, there is no way of knowing if any of the users lost connection with the management server.