by Dinesh Thakur

There are four basic components of Database Management System:


(i) Data: Raw facts which we want to feed in the computer.

(ii) Hardware: On which the data to be processed.

(iii) Software: The interface between the hardware and user, by which the data   will change into the information.

(iv) User: There are so many types of users some of them are application programmer, end case users and DBA.

Purpose of Database Systems:  

(i) To see why database management systems are necessary, let's look at a typical ``

File-Processing System'' supported by a conventional operating system.

The application is a savings bank:

• Savings account and customer records are kept in permanent system files.

• Application programs are written to manipulate files to perform the following tasks:

Debit or credit an account.

Add a new account.

Find an account balance.

Generate monthly statements.

(ii) Development of the System proceeds as follows:

• New application programs must be written as the need arises.

• New permanent files are created as required.

• But over a long period of time files may be in different formats, and

• Application programs may be in different languages.

(iii) So we can see there are problems with the Straight File-Processing Approach:

• Data Redundancy and Inconsistency:

Same information may be duplicated in several places.

All copies may not be updated properly.

• Difficulty in Accessing Data :

May have to write a new application program to satisfy an unusual request.

E.g. find all customers with the same postal code.

Could generate this data manually, but a long job.

• Data Isolation :

Data in different files.

Data in different formats.

Difficult to write new application programs.

• Multiple Users :

Want concurrency for faster response time.

Need protection for concurrent updates.

E.g. two customers withdrawing funds from the same account at the same time - account has $500 in it, and they withdraw $100 and $50. The result could be $350, $400 or $450 if no protection.

• Security Problems :

Every user of the system should be able to access only the data they are permitted to see.

E.g. payroll people only handle employee records, and cannot see customer accounts; tellers only access account data and cannot see payroll data.

Difficult to enforce this with application programs.

• Integrity Problems :

Data may be required to satisfy constraints.

E.g. no account balance below $25.00.

Again, difficult to enforce or to change constraints with the file-processing approach.

Above all problems lead to the development of Database Management Systems.


• An organized and comprehensiveness of recording the result of the firms activities.

• A receiver of data to be used in meeting the information requirement of the MIS users.

• Reduced data redundancy.

• Reduced updating errors and increased consistency.

• Greater data integrity and independence from applications programs.

• Improved data access to users through use of host and query languages.

• Improved data security.

• Reduced data entry, storage, and retrieval costs.

• Facilitated development of new applications program.

• Standard can be enforced: Standardized stored data format is particularly desirable as an old data to interchange or migration (change) between the system.

• Conflicting requirement can be handled.

Disadvantages :  

• It increases opportunity for person or groups outside the organization to gain access to information about the firms operation.

• It increases opportunity for fully training person within the organization to misuse the data resources intentionally.

• The data approach is a costly due to higher H/W and S/W requirements.

• Database systems are complex (due to data independence), difficult, and time-consuming to design.

• It is not maintain for all organizations .It is only efficient for particularly large organizations.

• Damage to database affects virtually all applications programs.

• Extensive conversion costs in moving form a file-based system to a database system.

• Initial training required for all programmers and users.