A service will be unavailable for the next two hours for unplanned maintenance.

Incident management is typically closely aligned with the service desk, which is the single point of contact for all users communicating with IT. When a service is disrupted or fails to deliver the promised performance during normal service hours, it is essential to restore the service to normal operation as quickly as possible.

https://www.bmc.com/blogs/itil-v3-incident-management/