Chapter9 - This chapter deals with the database approach to...

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Sheet1 Page 1 This chapter deals with the database approach to managing model is a particular philosophy whose objectives are supported by specific strategies, techniques, hardware, and software that are very different from those associated with flat-file environments. Chapter 1 drew a distinction between two general data management approaches: the flat-file model and the database model. Because the best way to present the virtues of the database model is by contrast with the flat-file model, the first section of this chapter examines how traditional flat-file problems are resolved under the database approach. Important features of modern relational databases are covered later in the chapter. The second section describes in detail the functions and relationship between four primary elements of the database environment: the users, the database management system (DBMS), the database administrator (DBA), and the physical database. The third section is devoted to an in-depth explanation of the characteristics of the relational model. A number of database design topics are covered, including data modeling, deriving relational tables from entity relationship (ER) diagrams, the creation of user views, and data normalization techniques. The fourth section concludes the chapter with a discussion of distributed database issues. It examines three possible database configurations in a distributed environment: centralized, partitioned, and replicated databases Overview of the Flat-File vs. Database Approach Many so-called legacy systems are characterized by the flat-file approach to data management. In this environment, users own their data files. Exclusive ownership of data is a natural consequence of two problems associated with the legacy-system era. The first is a business culture that erects barriers between organizational units that inhibit entity-wide integration of data. The second problem stems from limitations in flat-file management technology that require data files to be structured to the unique needs of the primary user. Thus the same data, used in slightly different ways by different users, may need to be restructured and reproduced in physically different files. Figure 9-1 illustrates this model. In the figure, the file contents are represented conceptually with letters. Each letter could signify a single data attribute (field), a record, or an entire file. Note also that data element B is present in all user files. This is called data redundancy and is the cause of three types of data management problems: data storage, data updating, and currency of Data Storage
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Chapter9 - This chapter deals with the database approach to...

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