(A).Data without sharing:
The most significant variation between file-based system and a database system is that data are shared.
There are three types of data sharing as follows:
(i.). sharing between functional Units: The data sharing suggests that people in different functional areas use general pool of data, each of their own applications. Lacking data sharing, the marketing group should have their data files, purchasing group theirs, accounting group theirs and so on. Each set benefits only from its own data. The combined data are additional valuable than the sum of data in separate files. Not only each group continue to have access to its own data but, within practical restrictions of control, they have way in to other data. The concept of combining data for common use is known as data integration.
(ii.). sharing data between different Levels of Users: Dissimilar levels of users need to share data.
Three different levels of users are usually distinguished: operations, middle management and executive. These levels correspond to the three unlike types of automated business systems that have evolved all through the past three decades:
(a. electronic Data Processing (EDP): EDP was first applied to the lower operational levels of the organization to automate paperwork. Its basic characteristics include these following points:
(1.). a focus on data, storage, processing and flows at operational level.
(2.). efficient transaction processing.
(3.). summary reports for management.
(b. management Information System (MIS): The MIS approach elevated the focus on information systems activities with additional emphasis on addition and planning of the information systems function. This includes:
(1.). an information focus aimed at the middle mangers.
(2.). an integration of EDP jobs by business function as in production MIS, marketing MIS,
Personnel MIS, etc.
(3.). Inquiry and report generation usually with database.
(c. decision Support System: DSS is focused still higher in organization with an emphasis on following characteristics:
(1.). decision focused, aimed at top managers and executive decision creators.
(2.). emphasis on flexibility, adaptability and fast response.
(3.). support for personnel decision-making styles of individual mangers.
Sharing data between Different Locations: A company with several locations has key data dist rebutted over a wide geographical area. Sharing these data is an important problem.
A centralized database is actually confined to a single location, controlled by a single computer. Mainly functions for databases are formed are accomplished added easily if database is centralized. That is, it is easier to inform, back up, query and control access to database if we know exactly where it is and what software controls it.
A distributed database system is made up of some database systems running at local sites connected by communication lines. A query is then no longer a single course controlled by one software module, but the set of cooperating processes running at several sites controlled by independent software modules. For a dispersed database system to function efficiently, adequate communication technology has to be available and the DBMS in the system has to be able to communicate while interacting with communications facilities.