Simple definition
Availability measures the proportion of time a service remains operational and accessible over a defined period under agreed conditions.
Purpose and use
Availability expresses how consistently a service remains usable over a defined period and under specified conditions.
How does it work?
Measurement can use service time or successful requests; document exclusions, scope and observation point.
Example and verification
For reporting, verify that the indicator detects reachable but unusable service, for example when a dependency blocks intended operations.
Points to watch
Percentages are not comparable when calendars, thresholds or exclusions differ. A powered-on server does not guarantee working user journeys.
In short
Availability should represent a measurable service commitment with shared definitions of success and interruption.