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Enterprise & Governance

Uptime

Uptime is the share of a period during which a service is available and functioning.

Uptime is typically expressed as a percentage and indicates how reliably a service remained available over a defined period. Meaningful evaluation should also consider planned maintenance, outages, and the method used to measure availability. The concept is closely related to Service Level Agreement and Monitoring.

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FAQ

Uptime

How are uptime and a service level agreement related?
The SLA sets a committed uptime and regulates measurement, exclusions, and consequences of missing it, usually service credits. Uptime is the metric, the SLA the contract around it. A credit does not replace lost revenue; resilience depends on architecture, not on contract wording.
How is uptime measured, and what does not count?
Usually through frequent checks by external monitoring services. What counts as downtime is defined differently by each provider; planned maintenance, force majeure, or errors in customer configurations are often excluded. A reachability check of the homepage will not detect failures in checkout or an API.
What does an uptime of 99.9 percent mean?
Mathematically, a service may be down about 8.8 hours per year; at 99.99 percent it is roughly 53 minutes. The percentage looks high but says nothing about when outages happen. One long outage during a sales launch weighs more than many short ones at night.