downtime

Downtime is the period when a system, service, or operation is unavailable or nonfunctional. In information technology, downtime can affect servers, networks, applications, and data services; in manufacturing and utilities it can affect equipment, production lines, and power delivery. Downtime can be scheduled, such as planned maintenance or software upgrades, or unscheduled, resulting from failures or incidents. Some downtime is partial, affecting only a subsystem, while other downtime results in a complete outage.

Common causes include hardware failures, software defects, misconfigurations, power outages, network connectivity problems, and external events such as natural disasters or cyberattacks. Human error and inadequate monitoring can also contribute. The impact depends on duration, scope, and the criticality of the affected service.

Metrics used to quantify downtime include uptime percentage, availability, mean time between failures (MTBF), and mean time to repair (MTTR). Service level agreements may specify acceptable downtime, often expressed as a percent of total time, for example 99.9% availability.

Mitigation strategies focus on reducing both the frequency and duration of downtime. Approaches include redundancy, failover and high-availability architectures, preventive maintenance, robust monitoring and alerting, regular backups, disaster recovery planning, and post-incident reviews to identify root causes and prevent recurrence. Effective downtime management aligns IT, operations, and business continuity goals.