In reliability theory and reliability engineering, the term availability has the following meanings: The degree to which a system, subsystem or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at an unknown, i.e. a random, time. Put, availability is the proportion of time a system is in a functioning condition; this is described as a mission capable rate. Mathematically, this is expressed as 100% minus unavailability; the ratio of the total time a functional unit is capable of being used during a given interval to the length of the interval. For example, a unit, capable of being used 100 hours per week would have an availability of 100/168. However, typical availability values are specified in decimal. In high availability applications, a metric known as nines, corresponding to the number of nines following the decimal point, is used. With this convention, "five nines" equals 0.99999 availability. Availability of a system is measured as a factor of its reliability – as reliability increases, so does availability.

Availability of a system may be increased by the strategy of focusing on increasing testability and maintainability and not on reliability. Improving maintainability during the early design phase is easier than reliability. Maintainability estimates are generally more accurate. However, because the uncertainties in the reliability estimates are in most cases large, it is to dominate the availability problem while maintainability levels are high. Furthermore, when reliability is not under control many and different sorts of issues may arise, for example: Lack of trained and capable repair personnel The need for detailed diagnostic procedures and other technical information Spare part availability Dead on arrival issues Lack of repair facilities and toolsThe problem of unreliability may become out of control due to the "domino effect" of maintenance induced failures after repairs and more and more increasing efforts of problem solving, re-engineering and service efforts. Only focusing on maintainability is therefore not enough!

If failures are prevented, none of the others are of any importance and therefore reliability is regarded as the most important part of availability! Reliability needs to be evaluated and improved related to both availability and the cost of ownership. A trade-off is needed between the two. There might be a maximum ratio between cost of ownership. Testability of a system should be addressed in the availability plan as this is the link between reliability and maintainability; the maintenance strategy can influence the reliability of a system, although it can never bring it above the inherent reliability. So, Maintainability and Maintenance strategies influences the availability of a system. In theory this can be unlimited if one would be able to always repair any fault in an infinitely short time; this is in practice impossible. Repair-ability is always limited due to testability and logistic considerations. Reliability is not limited. For high levels of system availability, the use of redundancy may be the only option.

Refer to reliability engineering. An availability plan should provide a strategy for availability control. Whether only Availability or Cost of Ownership is more important depends on the use of the system. For example, a system, a critical link in a production system – e.g. a big oil platform – is allowed to have a high cost of ownership if this translates to a minor increase in availability, as the unavailability of the platform results in a massive loss of revenue which can exceed the high cost of ownership. A proper reliability plan should always address RAMT analysis in its total context. RAMT stands in this case for Reliability, Maintainability/Maintenance and Testability in context to the customer needs; the simplest representation of availability is a ratio of the expected value of the uptime of a system to the aggregate of the expected values of up and down time, or A = E E + E If we define the status function X as X = { 1, sys functions at time t 0, otherwise therefore, the availability A at time t > 0 is represented by A = Pr

Ghost Shark is a 2013 supernatural horror film directed for the Syfy television network by Griff Furst. With Furst joined by Paul A. Birkett and Eric Forsberg for screenwriting, the film premiered on Syfy on August 22, 2013. Despite being panned critically, the movie had some success attracting attention from social media due to its fantastical premise, with websites such as Vulture.com commenting on moments from the film. A supposed sequel, Ghost Shark 2: Urban Jaws, was released on 1 July 2015, but the two movies are unrelated in terms of narrative other than both being films featuring killer sharks; when a great white shark eats the potential catch of a sport fisherman, the man and his daughter violently retaliate by sadistically torturing and killing the shark, whose corpse sinks to the bottom of an underwater cave and is subsequently resurrected as a ghost shark due to the cave's mysterious paranormal properties. Now hungry for revenge, the ghost shark eats his redneck killers along with the captain of their boat setting its sights on the rest of the local community in the seaside town of Harmony.

Due to the great white's new spectral form, it can attack and kill anyone as long as there is the smallest amount of water nearby, including coming out of a swimming pool, a bathtub, a bucket, a metal pipe, a drinking cup, killing many people in several locations. Though the terror is out of control, a group of young people trying to find answers end up having their pleas ignored. With the local mayor in the midst of his re-election campaign and other authorities unwilling to believe in such a state of events, teenager Ava Conte, who vows to put an end to the specter after it devours her father and several friends, teams up with a local lighthouse keeper named Finch, a drunken figure who claims to know the secrets to the shark's new-found form. After being arrested, harassed and otherwise impeded in their struggles, the group finally manages to lay the creature to rest once and for all. Mackenzie Rosman as Ava Reid Dave Randolph-Mayhem Davis as Blaise Parker Sloane Coe as Cicely Reid Jaren Mitchell as Cameron Stahl Richard Moll as Finch Lucky Johnson as Mayor Glen Stahl Tim Taylor as Deputy Hendricks Shawn C. Phillips as Mick Thomas Francis Murphy as Chief Martin Critical reception for Ghost Shark has been predominantly negative.

The film holds a rating of 29% on review aggregator website Rotten Tomatoes, based on seven reviews. For example, critic Jim Vorel wrote for Paste blasting the film as "a mind-numbing movie" featuring severe problems "rom its performances to its horrendous execution in the editing room", he concluded, "the film violates the most crucial rule of trashy filmmaking— you can be stupid, but don’t be boring." Vorel criticized the fact that the character of Cicily, played by Sloane Coe, is filmed in a sexually suggestive manner in several scenes despite the fact that she's identified as being too young to have a driver’s license. One of the rare mixed to positive reviews for Ghost Shark came from Horrornews.net, with the film given a five out of ten score and labeled as featuring both "pecial effects that would make a film student cringe" but a "well experienced cast mixed with fresh faced and eager newcomers." The film was compared, both positively and negatively, to an episode of one of the Scooby-Doo cartoons.

In spite of being panned critically, the movie had some success attracting social media attention, with websites such as Vulture.com commenting on moments from the film. Ghost Shark 2: Urban Jaws List of killer shark films Ghost Shark on IMDb Ghost Shark at Horrordrome

The 1993 Pot Black was the third of the revived professional invitational snooker tournament, the 21st series altogether and the last series of Pot Black in its traditional form. Recording broadcast in autumn; the tournament was held at Pebble Mill Studios in Birmingham, had reverted to the traditional format after the 1992 "Timeframe" was unpopular with viewers and players. It featured sixteen professional players in a knock-out system. All matches until the semi-final were one-frame shoot-outs, the semi-final was an aggregate score of two frames and the final being contested over the best of three frames. Broadcasts were shown on Monday afternoons on BBC1 except the semi-finals and final were for three days and the series started at 15:05 on Monday 6 September 1993. David Vine was the new presenter for the series replacing Eammon Holmes and Ted Lowe remained in the commentary box with some of the players as co-commentators while John Williams refereed the series; the final was won by Steve Davis beating Mike Hallett 2–0 and winning the Pot Black title for the fourth time beating John Spencer and Eddie Charlton's record of three titles