Availability

The process of breaking down system reliability and availability objectives to subsystems and major components. Reliability allocation specifies clearly stated reliability goals for all elements of an item. This information is useful when seeking suitable elements (parts or subsystems). It gives a means to compare the reliability performance of subsystems or elements to a specific and measurable objective.

Various specific elements have been defined by different authors, yet they generally comprise the concepts of availability, dependability, and capability.

The mathematical limit as time tends to infinity for the availability function.

A measure of the degree to which an item is operable and capable of performing its required function at any (random) time during a specified mission profile, given item availability at the start of the mission. See Availability.

A measure of availability that includes only the effects of an item design and its application, and does not account for effects of the operational and support environment. Sometimes referred to as "intrinsic"availability.