Nedetidstolerans

Nedetidstolerans is the maximum amount of downtime that a system, service or infrastructure is permitted to experience within a defined period, as agreed in a contract or internal policy. The concept is used in reliability engineering and service-level agreements to set expectations and guide investments in resilience.

In practice, nedetidstolerans is expressed as a time threshold (for example, X hours per year or Y minutes per month) or as a target availability percentage (such as 99.9%). The downtime is measured from monitoring data and typically excludes planned maintenance, deployments, force majeure, and other defined exemptions. Availability is calculated as (total time - downtime) / total time over the measurement period.

Setting a low tolerance increases requirements for resilience, such as redundancy, failover, and proactive monitoring, but raises costs. A higher tolerance lowers costs but increases the risk of interruptions for users. The threshold is central to service-level agreements and may trigger service credits, remediation steps, or penalties if not met.

Common examples include 99.9% availability, which corresponds to about 8.76 hours of downtime per year, or roughly 43.2 minutes per month, depending on the measurement period. Planned maintenance windows are frequently excluded from the calculation.

Measurement and governance involve using monitoring tools and incident management processes to track downtime, define what counts as downtime, specify exclusions, and support continuous improvement in reliability and service delivery. Nedetidstolerans thus reflects an organization’s risk tolerance and investment in resilience.

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