Chracteristics of centralized database
Prior to the popular acceptance of DDBMSs, corporations normally relied on centralized databases designed to serve very structured information requirements. These centralized databases had some characteristics in common. First, they ran on powerful and expensive hardware that could handle very large portions of a firm’s data reliably. Second, they were administered by a small number of well-trained people who could manage the organization’s complex mainframe or minicomputer. Third, the dedicated data lines forming the corporate wide area network (WAN) had to be highly reliable and have a large capacity, because any downtime will preclude at least one site from operating, and every operation had to be transmitted to and from the central database in real time. These centralized databases could provide adequate performance to firms able to work around their shortcomings. These shortcomings include the lack of flexibility in the application of the firm’s information and the requirement to implement a single point of failure for the entire enterprise.
This section explores the lessons learned about the limitations of centralized database systems over the thirty years they have been in general use. First the business forces are explored. Each of these business issues has generated information technology requirements that distributed database architectures are uniquely capable of supporting. Second, the technology issues are explored. These have come about from advances in information technology that have made the centralized database model less relevant in today’s organizations.