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Direct changeover is one of the methods to change from an existing system to a new one. thumb This is the simplest methods of changeover. Imagine a new checkout system for a supermarket. If the implementation is done by direct changeover, then the supermarket will be closed for one night, all the old checkouts will be taken out, the new ones will be installed and the supermarket will be ready to open the next day. Although this is a simple method, it takes a lot of planning. All the files have to be ready to load, all the workers need to have been trained in advance and the system must have been properly tested. If the checkouts do not work when they are switched on, the store will have to close because they cannot go back to the old system. This is how the UK stock market was computerized in the 1980s. The old market closed on Friday night and the computers were all switched on the following Monday morning. Unfortunately, there was an error in the software, which made all the computers sell shares and carry on selling them. By the time human beings had intervened to stop the computers, half of the value of companies had been wiped off the stock market and many people had been ruined. Other methods of changeover include phased implementation and parallel running. == References == 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Direct changeover」の詳細全文を読む スポンサード リンク
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