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✈ | Airbus signs support service for Egyptian Air Force C295

Photo Egyptian Air Force C295

Airbus signs support service for Egyptian Air Force C295

If you write the contents roughly
The contract will allow the Egyptian Air Force to receive support when and where it is needed, optimizing the aircraft's availability and mission performance.

Airbus Defense and Space on Thursday, April 2021, 4 about the Egyptian Air Force and C15 ... → Continue reading


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Mission performance ability


RASIS > Usability
Information security > Usability

Usability(Kayosei, English: availability; availability) Is the degree and ability of the system to operate continuously.

For availabilityreliability-MaintainabilityIncludingRAS,furtherMaintainability-安全 性IncludingRASISSometimes called.


Availability is in English availability It is a translation for.Indicates the degree of "usability" from the user's point of view.The definitions in the major standards are as follows.

  • JIS X 0014: 1999 "Information Processing Terms-Reliability, Maintainability and Availability"
The ability of a functional unit to perform a required function at a given time or for a certain period of time under certain conditions when the necessary external resources are given.
  • JIS X 5004: 1991 "Basic reference model for interconnection between open systems-safety protection system"
Properties that can be accessed and used when requested by an authorized entity
  • JIS Q 20000-1: 2012 "Information Technology-Service Management-Part 1: Service Management Requirements"
The ability of a service or service component to perform the requested function over a pre-agreed time or period.

Regarding reliability and maintainability, which are the other two of RAS, reliability means that hardware and software fail less frequently and the period of failure is short, availability means that users can use it, and maintainability means maintenance. Refers to being easy to do.

These three are often confused, but they need to be considered separately from the perspective of troubleshooting.In general, the lower the reliability and the more failures, the lower the availability.However, even if a failure occurs, the impact on availability can be minimized if it is made redundant or if the effects of the failure are mitigated and localized successfully.In addition, if maintainability is low, repair time when a failure occurs, inspection and backup time during normal operation, etc. become long, and overall availability is limited.


The idea of ​​using the three elements of RAS as evaluation indicatorsIBMIs largeComputer(main frame)ofSystem / 370Series1970It begins with the announcement in June. System / 61964Was a general-purpose computer developed and sold by IBMSystem / 360It is the successor to the series. IBM has adopted a new RAS concept in this new System / 370 model and appealed for its new value as a product.[1].

At that time, they competed for services with the same functions and performance as IBM computers.Fujitsu日立2 companies are also IBMCompatible machineAsM seriesShared the market.From the standpoint of a compatible machine, this M series also incorporates the RAS function sung by IBM.[2]..Due to such circumstances, with RAS, after that, "I"When"SWas addedRASISIs currently widely used not only in the field of computersAcronymIt became a word as.

English adjectives available Has meanings such as useful and available[3], Its noun availability Japanese corresponding to is said to be effective and useful,[4]When IBM Japan launched the System / 370 series to the Japanese market, "Availability in RAS sung by IBM in the United States, which is the head office, is a new word with novelty regardless of the translation of the English-Japanese dictionary.UsabilityWas called.

Occupancy rate

The numerical representation of availabilityOccupancy rateThe probability that repairable systems, equipment, parts, etc. maintain their functions at a specific moment (instantaneous operating rate), or the probability that they maintain their functions within a specified period of time. (Average utilization rate).The abbreviation is A.

Occupancy rate A and available time (MTBF), Inoperable time (MTTR) Is as follows.

Annual downtime
Occupancy rateInoperable time
99.9999%32 秒
99.999%5 minutes 15 seconds
99.99%52 minutes 34 seconds
99.9%XNUM X hours X NUM X minutes
99%3 days 15 hours 36 minutes

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