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Model 204 is a database management system for IBM and compatible mainframe computers, “born” 1965 October 13,〔 〕〔 and first deployed in 1972. It incorporates a programming language and an environment for application development. Implemented in assembly language〔(【引用サイトリンク】url=http://sirius-software.com/m204.html )〕 for IBM System/360 and its successors, M204 can deal with very large databases and transaction loads of 1000 TPS.〔 Model 204 relies on its own type of bitmap index, originally devised by Professor Patrick E. O'Neil, and also combines the use of hash table, B-tree, and record list technologies to optimize speed and efficiency of database access. Although M204 is a pre-SQL (and pre-relational) database product, it is possible to manually map the files of an M204 database to approximate SQL equivalents and provide some limited SQL functionality using Model 204 SQL Server. Model 204 is most commonly used in government and military applications. Among other things, it runs Australia's social security system (Centrelink). It is used commercially in the UK by Marks & Spencer. It is also used at the Ventura County Property Tax system in California, the Harris County, Texas, Justice Information Management System, and in the New York City Department of Education's Automate The Schools system. An informal list of past and present Model 204 users, compiled in 2010, identified more than 140 organizations worldwide. It is a product of Computer Corporation of America (CCA). In April 2010, CCA was acquired by Rocket Software, a Boston-based developer of enterprise infrastructure products.〔http://www.ebizq.net/news/12526.html; acquired June 13, 2010〕 Add-on products are available from Sirius Software, Inc. Database Programmer's Toolkit is a freeware PC-based emulation. == See also == *Entity-attribute-value model 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「Model 204」の詳細全文を読む スポンサード リンク
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