Hi everyone ,I received text and emails from my friends to tell them about DATABASE SYSTEM.So my todays topic is all about database system. First of all i would like to describe database system, a database system is a collection of data as well as program required to manage that data.A database system is a computerized record keeping system.The main purpose of this system is to maintain data and provide it to user when it is required.

The major components of database system are as follows:: 1:DATA .Data is the most important component of database system.Data is a collection of facts placed in a database.The basic purpose of a database system is to store,maintain and access data for users. 2:HARDWARE.The physical components of a computer system are called hardware which performs different tasks such as input,output, and processing. Some important hardware components are as follows: (i)Secondary storage (ii)I/O devices (iii) processors (iv)main memory 3: SOFTWARE: Software is a collection of programs used by computer.The most important software is DBMS itself.It uses various types of software to enable the database system work properly . 4:PERSONNEL:It includes Database Administrators who manage DBMS use and ensure database function properly.It also includes application programmers who write application programs to access data from database..It also includes End users who use application programs to access data from database.they may be clerks,directors and managers.

First objective of Database system is Data integration.The data in file system is stored in separate files.An important objective of database is to solve potential problems.The data in database may be located at different computers physically but connected through data communication links.Next objective of database is Data integrity to ensure reliability and accuracy of data.Integrity rules are applied for the purpose to keep the data consistent and accurate.These rules are check on the incoming data input and it maintains the quality of data stored.For example an employee ID is entered as “4663464344”,this value should not be entered again and the same ID should not be assigned to two or more persons or employees.Third objective is to ensure the independence of data from application programs .The changes in data storage structures and operations can be made without changes in application programs.

Now I will move towards various types of database models.Here a question will arouse in your mind that what is database model?Database model is a set of standards and rules that describes how data is organised by database system and also define how users view organisation of data.First type of logical database model is Hierarchical Model which arranges data and records in hierarchy just like an organizational chart.Each typed record in this model is called a segment or node.A node represents particular entity.The top most node is called a root.A higher level node is called parent and lower level node called Child.A parent node may have multiple child nodes but a child node have only one parent node.this structure of nodes is called inverted tree.

2nd type of model is Network Model which is similar to hierarchical model.Difference is that child node can also have multiple parent nodes.The child nodes are represented by arrows in network model.It requires more complex diagram to represent a database.

3rd is the Relational model which is most commonly used model.It is more flexible and efficient than other two models explained above.It consists of simple relations for which a term can be used is table.Relation represents specific entity and used to store information and data of that particular entity.Relationship between entities is shown by diagram which is similar to network model diagram and relation is based on data of entities.

Now let me explain Database Management system also abbreviated as (DBMS). Data management system is a collection of programs that are used to maintain and access database in a convenient and efficient way.DBMS is an improvement over the traditional File management system.

First objective of database management is SHARE ABILITY which means data is shared by different people at the same time.Data is stored at a central place from which different users can access data at different locations and reduces storage costs and provides data consistency.2nd objective is AVAILABILITY which means data must be accessible to users easily.data must be available when they require it.3rd is EVOLVE ABILITY which means DBMS must be able to change due to increase in user requirements or change in the technology.The change in database may occur in two ways.It may change by contents or by structures.For example,the structure of the database may be changed if the operation of an organisation is expanded.4th is Database integrity as explained above,data is shared between different users so some measures must be maintained to ensure data integrity.Main objectives of database integrity are (i) protecting the existence of database(ii) Maintaining the quality of database(iii) Ensures the privacy of data base.