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Unformatted text preview: P ART E IGHT T raditionally, the data processing function was organized in a centralized fash- ion. In a centralized data processing architecture, data processing support is provided by one or a cluster of computers, generally large computers, located in a central data processing facility. Many of the tasks performed by such a facility are initiated at the center with the results produced at the center.An example is a payroll application. Other tasks may require interactive access by personnel who are not physically located in the data processing center. For example, a data entry function, such as inventory update, may be performed by personnel at sites throughout the or- ganization. In a centralized architecture, each person is provided with a local terminal that is connected by a communications facility to the central data processing facility. A fully centralized data processing facility is centralized in many senses of the word: • Centralized computers: One or more computers are located in a central facil- ity. In many cases, there are one or more large mainframe computers, which re- quire special facilities such as air conditioning and a raised floor. In a smaller organization, the central computer or computers are large minicomputers, or midrange systems. The iSeries from IBM is an example of a midrange system. • Centralized processing: All applications are run on the central data processing facility.This includes applications that are clearly central or organization-wide in nature, such as payroll, as well as applications that support the needs of users in a particular organizational unit.As an example of the latter, a product design department may make use of a computer-aided design (CAD) graphics package that runs on the central facility. • Centralized data: All data are stored in files and databases at the central facility and are controlled by and accessible by the central computer or computers.This includes data that are of use to many units in the organization, such as inventory figures, as well as data that support the needs of, and should be used by, only one organizational unit.As an example of the latter, the marketing organization may maintain a database with information derived from customer surveys. Such a centralized organization has a number of attractive aspects. There may be economies of scale in the purchase and operation of equipment and software. A large central DP shop can afford to have professional programmers on staff to meet Distributed Systems 707 M16_STAL6329_06_SE_C16.QXD 2/22/08 8:44 PM Page 707 708 PART 8 / DISTRIBUTED SYSTEMS the needs of the various departments. Management can maintain control over data processing procurement, enforce standards for programming and data file structure, and design and implement a security policy....
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- Spring '10