Database Management System
A Database is a well organized collection of data that are related in a meaningful way which can be accessed in different logical orders but are stored only once. The data in the database is therefore integrated, structured and shared.
The main features of data in a database are :
- It is well organized
- It is related
- It is accessible in different orders without great difficulty
- It is stored only once
A DBMS is a software that allows creation, definition and manipulation of database. A database management system stores data in such a way that it becomes easier to retrieve, manipulate, and produce information.Here are some examples of popular DBMS, MySql, Oracle, Sybase, Microsoft Access and IBM DB2 etc.
- Data Persistence
Data persistence means that in a DBMS all data is maintained as long as it is not deleted explicitly. The life span of data needs to be determined directly or indirectly be the user and must not be dependent on system features. Additionally data once stored in a database must not be lost. Changes of a database, which are done by a transaction, are persistent. When a transaction is finished even a system crash cannot put the data in danger.
Consistency is a state where every relation in a database remains consistent. There exist methods and techniques, which can detect attempt of leaving database in inconsistent state. A database management system can provide greater consistency as compared to earlier forms of data storing applications like file-processing systems.
- Isolation of data and application
It makes data independent of application programs. That is one can add, change, and delete fields from database without affecting existing programs.
- Multi-user and Concurrent Access
Sharing of the data takes place amongst the different type of the users and the applications. Database management system supports multi-user environment and allows them to access and manipulate data in parallel mode. Sometimes it is necessary to restrict the transactions, when multiple user attempts to access the same data items; because of an unawareness of transaction processing.
- Multiple views
Database management system offers multiple views for different users. A user who is in the purchase department will have a different view of database than a person working in the sales department. This feature enables the users to have a concentrate view of the database according to their requirements.
- Query Language
Database management system is equipped with query language, which makes it more efficient to retrieve and manipulate data. A user can apply as many and as different filtering options as required to retrieve a set of data. Traditionally it was not possible where file-processing system was used.
- Real-world entity
A recent Database management system is more realistic and uses real-world entities to design its architecture. It uses the behaviour and attributes too. For example, a school database may use students as an entity and their age as an attribute.
- Relation-based tables
Database management system allows entities and relations among them to form tables. A user can understand the architecture of a database just by looking at the table names.
- Reduce Redundancy
Database management system follows the rules of normalization, which splits a relation when any of its attributes is having redundancy in values. Normalization is a mathematically rich and scientific process that reduces data redundancy.
Not all users of the system have the same accessing privileges. DBMS should provide a security subsystem to create and control the user accounts.