What is the term for the operational availability of a system, often stated as a percentage?

The term that refers to the operational availability of a system, often expressed as a percentage, is "availability." This concept is crucial in assessing how often a system is operational and able to provide its intended functions without interruptions. Availability encompasses both the reliability of the system—meaning it can perform consistently without failure—and the maintainability, which refers to how quickly and effectively it can be repaired if there is a fault.

When availability is represented as a percentage, it indicates the proportion of time that the system is operational compared to the total time it is expected to be available. For example, a system with 99% availability is operational 99% of the time over a specified period. This metric is vital in a variety of sectors, particularly in IT services, where uptime is critical for business operations.

The other terms mentioned do not accurately define operational availability. Reliability focuses more on the ability of a system to perform consistently over time, while performance refers to how well a system operates in terms of speed, efficiency, and responsiveness. Normativity is not a standard term used in this context and does not relate to operational availability.