A. Data without sharing:
The mainly significant difference between a file-based system and a database system is that data are shared.
There are three kinds of data sharing:
(i)Sharing between Functional Units: The data sharing proposes that people in various functional areas use common pool of data, each of their own requests. Without data sharing marketing group might have their data files, purchasing group theirs, accounting group theirs and so on. Each group benefits only from its own data. The combined data are more important than sum of the data in separate files. Not only does each group carry on to have way in to its own data but, within reasonable restrictions of control, they have entrance to other data as well. The concept of merge data for common use is known as data integration.
(ii)sharing data between Different Levels of Users: Different levels of users need to share data.
Three different points of users are normally distinguished: operations, middle management and executive. These levels correspond to three different types of automated business systems that have evolved during 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:
1. ) A focus on data, storage, processing and flows at operational level.
2. ) Efficient t 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 integration and planning of information systems function. This includes following points:
1. ) An information focus aimed at middle managers.
2. ) An integration of EDP jobs by business function such as production MIS, marketing MIS, Personnel MIS.
3. ) Inquiry and report generation usually with database.
c. Decision Support System: DSS is focused still senior in the organization with emphasis on the following characteristics:
1. ) Decision focused, aimed at top managers and executive decision creators.
iii)sharing data between Different Locations: A company with several locations has important data dist rebutted over a wide geographical area. Sharing these data is an important problem.
A middle database is actually confined to a single location, controlled by a single computer. Most functions for databases are formed are accomplished more simply if database is centralized. That is, it is easier to revise, back up, query and control access to a database if we know accurately where it is and what software controls it.
A distributed database system is made up of some database systems running at local sites linked by communication lines. A query is then no longer a single process controlled by one software module, but a set of cooperating methods running at some sites controlled by independent software modules. For a distributed database system to function efficiently adequate communication technology have to be available and the DBMS in system must be able to communicate while interacting with communications facilities.