Database Management System

1. Introduction
 What is Database Management System?
A database management system (DBMS) is a collection of interrelated data and a set of programs to access
those data. The collection of data, usually referred to a database, contains information relevant to an
enterprise.
 Goals of a DBMS
1. The primary goal of a DBMS is to provide an environment that is both convenient and efficient for people
to use in retrieving and storing information.
2. Database systems are designed to manage large bodies of information. Management of data involves
both defining structures for storage of information and providing mechanisms for manipulation of
information.
3. The database system must ensure the safety and security of the information stored, despite system
crashes or attempts at unauthorized access.
4. The system must avoid possible anomalous results if data are to be shared among several users.
1.1 Database System Applications
Databases are widely used. Some representative applications are:
1. Banking: For customer information, accounts, loans, banking transactions.
2. Airlines/Railways/Road Transport: For ticket reservation, schedules and routes.
3. Universities: For student information, courses and grades (education management).
4. Credit card transaction: For purchases on credit card, monthly statement generation
5. Telecommunication: For keeping records of call made, generating monthly bills, maintaining balances
on prepaid calling cards, storing information about the communication networks.
6. Finance: For storing information about holdings, sales, and purchases of financial instruments such as
stocks and bonds.
7. Sales: For customer, product and purchase information.
8. On-line retailers: For sales data model above plus on-line order tracking, generation of recommendation
lists and maintenance of on-line product evaluation.
9. Manufacturing: For management of supply chains and for tracking production of items in factories,
inventories of items in warehouses/stores and order for items.
10. Human resources: For information about employees, salaries, payroll taxes and benefits and for
generation of pay checks.
11. Internet: Internet is the major repository of database.

2.  Some Commercial Database Management Systems
1. Oracle – Oracle 8i, Oracle9i, Oracle 10g
2. Microsoft SQL Server
3. IBM DB2/DB2UDB
4. Informix
5. Sybase
6. MySQL
7. Ingress
8. PostgreSQL
 For Personal Computers
1. Microsoft Access
2. FoxPro
3. dBase
1.2 Purpose of Database Systems (Database Systems Vs File Systems)
Ordinary file system has a number of major drawbacks:
1. Data redundancy and inconsistency
- Multiple file formats, duplication of information in different files
2. Difficulty in accessing data
- Need to write a new program to carry out each new task
3. Data isolation
- Multiple files and formats
4. Integrity problems
- Integrity constraints (e.g. account balance > 0) become part of program code rather than being stated
explicitly
- Hard to add new constraints or change existing ones
5. Atomicity problems
- Failures may leave database in an inconsistent state with partial updates carried out. E.g., transfer of
funds from one account to another should either complete or not happen at all
6. Concurrent-access anomalies
- Needed for system performance and faster response
- Uncontrolled concurrent accesses can lead to inconsistencies. E.g. two people reading a balance and
updating it at the same time
7. Security problems
- Not every user of the database system should be able to access all the data. Hard to provide user access

3. to some data, but not all
Database systems offer solutions to all these problems
A. S. M. Shafi
Lecturer
Department of Computer Science and Engineering
Khwaja Yunus Ali University
Enaytpur, Sirajgonj-6751, Bangladesh