Level of uptime (also called availability)
|“||describes the time in a defined period the service was available, over the total possible available time, expressed as a percentage.||”|
"Some cloud services specify that the service will be unavailable for specified periods for maintenance. It is common for the stated level of uptime to exclude these maintenance periods. In this case Uptime = Total Possible Available Time – (Total Downtime – Maintenance Downtime)."