Glossary
Maintenance window
A defined period during which a system may be taken down or changed, agreed with its owner and known to everyone the outage affects.
Also calledservice window · outage window · change window
A defined period — start time, end time, date — in which a change that may affect availability is permitted. The window is not just an hour in a calendar: it carries who approved it, what may be done inside it, and what happens if something fails.
In a regulated organisation the window is also an evidence artefact. A window agreed verbally and executed perfectly looks, in hindsight, exactly like an unapproved change.
What makes a window well-formed
- A start and an end, not "overnight".
- A named owner who approved it, with a timestamp.
- A scope — which hosts, which patch.
- A rollback plan — what happens if the service does not come back.