IT officer-1

1.   Database :   Collection of data is referred to as a database.

2.   DBMS :  A database management system is a set of programs to manage data.

3.   DATA REDUDANCY:   Different files have different formats of programs written in different programming languages by different users. So the same information may be duplicated in several files. It may lead to data inconsistency and known as data redundancy.

4.  Data isolation : Data is scattered in various files; so it gets

isolated because file may be in different formats.

5.  Security :   Not every user of the database system should be able to access all data. Data base should be protected from access by unauthorized users.

6.  DATA ABSTRACTION :  Major purpose of DBMS is to provide users with abstract view of data i.e. the system hides certain details of how the data are stored and maintained. This is called data – abstraction .

7.  3 levels of abstraction :

A.  VIEW LEVEL OF DATA ABSTRACTION :

View provides security mechanism to prevent user from accessing certain parts of database.

EG:  GENERALLY ... IN A PDF FILE ... WE CAN’T CHANGE DATA BUT CAN ONLY VIEW IT.

 B.  Logical level of data abstraction:

This level hides what data are actually stored in the database and what relationship exists among them.

EG:  DIFFERENT TYPES OF USERS IN AN OPERATING SYSTEM

C. Physical level of data abstraction:

This s the lowest level of abstraction which describes how data are actually stored.

EG: TO CREATE PARTITIAN LIKE C AND D DRIVES.