Availability
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- For availability as a form of cognitive bias, see availability heuristic.
In telecommunications, the term availability has the following meanings:
1. The degree to which a system, subsystem, or equipment is operable and in a committable state at the start of a mission, when the mission is called for at an unknown, i.e., a random, time.
Note 1: The conditions determining operability and committability must be specified.
Note 2: Expressed mathematically, availability is 1 minus the unavailability.
2. The ratio of (a) the total time a functional unit is capable of being used during a given interval to (b) the length of the interval.
Note 1: An example of availability is 100/168 if the unit is capable of being used for 100 hours in a week.
Note 2: Typical availability objectives are specified either in decimal fractions, such as 0.9998, or sometimes in a logarithmic unit called nines, which corresponds roughly to a number of nines following the decimal point, such as "five nines" for 0.99999 reliability.
Source: from Federal Standard 1037C in support of MIL-STD-188
See also
External links
- Reliability and Availability Basics (http://www.eventhelix.com/RealtimeMantra/FaultHandling/reliability_availability_basics.htm)
- System Reliability and Availability (http://www.eventhelix.com/RealtimeMantra/FaultHandling/system_reliability_availability.htm)de:Verfügbarkeit