Wednesday, June 1, 2011

Introduction to Database

What is File Based Systems?
File Based Systems are collection of application programs that perform services for the end user. We can give example likes reports. Filed based systems make each program defines and manages its own data.

Limitation of File Based Approach:

1. Separation and isolation of data.
Each program maintains its own set data. It means data in one program is different in another programs. Users of one programs may be unaware of potentialy useful data held by another programs.

2. Duplication of Data.
Same data is held by different programs. It makes wasted space and potentially different values and/or different formats for the same time. 

3. Data Dependence.  
File structure  is defined in the program code.

4. Incompatible file formats.
Programs are written in different languages, and so cannot easily access each other files.

5. Fixed Queries.
Programs are written to satisfy particular functions. Becasuse of that, any new requirements needs a new program.

What is Database?
A shared collection of logically related data and a description of this data, designed to meet the information needs of an organization. Its likes system catalog (meta data) provides description of data to enable program – data independence. Database make logically related data comprises entities, attributes, and relationships of an organization’s information.

What is Database Management Systems?
A software system that enables users to define, create and maintain the database and that provides controlled access this database.

Advantages of DBMSs :
1. Balanced confliting requirements.
2. Improved data accessbility and responsiveness.
3. Increased productivity.
4. Improved maintenance through data independence.
5. Increased concurrency.
6. Improved Back Up and Recovery services