On the other hand if it is too low the reaction may

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ystems Another development in the database area that was the result of the proliferation of computer networks was that of distributed database systems. A distributed database system seamlessly integrates multiple databases located on different computers. These computers may be located in the same building or may be geographically far apart (such as in different cities). Note that unlike a clientserver database system in which there is only one database, a distributed database system has multiple databases integrated together to serve as a single database. The main motivation behind using a distributed database system is to store data in the most convenient places within a computer network, depending on data entry requirements, storage capacity availability, processing load requirements, data security requirements, and so on. For example, as shown in Figure 16.21, a distributed database system might integrate employee databases of different departments of an organization that are located in different cities. Each department's database stores the records of the employees working in that department. A distributed database management system functions in such a manner that the multiple distributed databases managed by it appear as a single centralized database to the end users. That is. a user making a request would not be concerned about the source of the data or how they are retrieved. For example, in the distributed database system of Figure 16.21, a user can simply make a single request for a sorted list of all female employees in the organization who are more than 40 years old. The distributed database management system takes care of sending this request to all the four databases, then accumulating the results, sorting it, and presenting it to the user. All this is done internally without the knowledge of the user making the request. Active Database Systems Traditional database management systems are passive in the sense that commands are executed by the database (such as, query, update, delete) as and when requested by the u...
View Full Document

This document was uploaded on 04/07/2014.

Ask a homework question - tutors are online