Geographic Information Systems: An Introduction, 3rd Edition

12.2 Distributed Databases

The modern data network has made possible decentralized database solutions. Distributed database systems constitute a special decentralized solution (Figure 12.5). A system with a distributed database comprises several databases on different computers closely integrated with the assistance of a network and treated as one unit. Users experience this as if they are working with one database. The viewing solution (Figure 12.4d) is a “light” version of distributed databases.

Subdatabases may have different database management systems; copies of the same data can be found in several of these subdatabases and the data can be stored in different formats. This level of complexity makes particularly high demands on control routines in the joint database management system. Distributed solutions have special requirements with respect to common data models, routines for maintaining and checking data quality, routines for access control, and so on. All this can result in the system being relatively expensive to run. However, there are a number of advantages, such as increased total capacity, increased reliability and access to data, increased efficiency and flexibility, and the advantages of pooling (sharing) resources.

Figure 12.5

Storage can be divided among several producers or users. The manipulation (search, selection, transport, and organization) of common data ...