計算機(jī)外文翻譯---數(shù)據(jù)庫管理系統(tǒng)的介紹-管理系統(tǒng)-資料下載頁
2025-05-11 17:25本頁面
【導(dǎo)讀】起來的一組數(shù)據(jù)或信息，其目的是為了便于計算機(jī)快速查詢及檢索。索，修改和刪除。含一個或多個字段。字段是數(shù)據(jù)存取的基本單位。實體，其中的一個字段通常表示與實體的某一屬性相關(guān)的信息。或選擇，以實體對某一類數(shù)據(jù)的檢索，也可以生成報表。所有數(shù)據(jù)庫中都有復(fù)雜的數(shù)據(jù)關(guān)系及其鏈接。是應(yīng)用程序員，管理員及其他需要信息的人員和各種操作系統(tǒng)程序）。DBMS可組織，處理和表示從數(shù)據(jù)庫中選出的數(shù)據(jù)元。預(yù)料的問題做出回答。簡言之，DBMS將“管理”存儲。的數(shù)據(jù)項，并從公共數(shù)據(jù)庫中匯集所需的數(shù)據(jù)項以回答非程序員的詢問。在提高數(shù)據(jù)庫管理系統(tǒng)的價值和有效性方。，他們利用數(shù)據(jù)庫系統(tǒng)領(lǐng)先于競爭對手。顯示，維護(hù)，打印，查找，選擇，排序和更新等操作。數(shù)據(jù)庫管理方法，使用表作為數(shù)據(jù)結(jié)構(gòu),稱之為關(guān)系模型.最新的數(shù)據(jù)庫管理方法是使用對象模型，記錄由被稱作對象的實體來描述，分布式數(shù)據(jù)庫的一個目的是訪問數(shù)據(jù)信息時不必考慮其他位置。
【正文】 tralized control , many of the problems of data integrity that we mentioned earlier are solved . But today’s personal 9 puters, departmental puters, and distributed processing require puters and their applications to municate with each other on a more equal or peertopeer basis. In a database, the client/server model provides the framework for distributing databases. One way to take advantage of many connected puters running database applications is to distribute the application into cooperating parts that are independent of one anther. A client is an end user or puter program that requests resources across a work. A server is a puter running software that fulfills those requests across a work . When the resources are data in a database ,the client/server model provides the framework for distributing database. A file serve is software that provides access to files across a work. A dedicated file server is a single puter dedicated to being a file server. This is useful ,for example ,if the files are large and require fast access .In such cases, a miniputer or mainframe would be used as a file server. A distributed file server spreads the files around on individual puters instead of placing them on one dedicated puter. Advantages of the latter server include the ability to store and retrieve files on other puters and the elimination of duplicate files on each puter. A major disadvantage , however, is that individual read/write requests are being moved across the work and problems can arise when updating files. Suppose a user requests a record from a file and changes it while another user requests the same record and changes it too. The solution to this problems called record locking, which means that the first request makes others requests wait until the first request is satisfied . Other users may be able to read the record, but they will not be able to change it . A database server is software that services requests to a database across a work. For example, suppose a user types in a query for data on his or her personal puter . If the application is designed with the client/server model in mind ,the query language part on the personal puter simple sends the query across the work to the database server and requests to be notified when the data are found. Examples of distributed database systems can be found in the engineering world. 10 Sun’s Network Filing System(NFS),for example, is used in puteraided engineering applications to distribute data among the hard disks in a work of Sun workstation. Distributing databases is an evolutionary step because it is logical that data should exist at the location where they are being used . Departmental puters within a large corporation ,for example, should have data reside locally , yet those data should be accessible by authorized corporate management when they want to consolidate departmental data . DBMS software will protect the security and integrity of the database , and the distributed database will appear to its users as no different from the nondistributed database .
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