DATABASE MANAGEMENT

DATABASE MAGEMENT SYSTEM 1

WHAT IS DATABASE MANAGEMENT ?


SOME BASIC CONCEPT

What is a data? Data is collection of facts and figures which can be processed to produce information.

What is a database? A database is a collection of data


DATA BASE MANAGEMENT SYSTEM (DBMS)

A DBMS is a collection of data which

Provide management of databases Used to store, update, retrieve,manipulate &

helps to produce information. Control access to data Provide convenient & efficient to retrieve data Supports secure, atomic access to very large

amounts of data.


provide concurrent access (different users at the same time).

Provides an interface between users and the database

Backup and Recovery in event of a system failure.

Security - password allocation and access rights to particular layouts.


APPLICATION SALES: For customer, product, and purchase

information. ACCOUNTING: For payments, receipts, account

balances, assets and other accounting information

HUMAN RESOURCES: For information about employees, salaries, payroll taxes and benefits, and for generation of paychecks.

BANKING: For customer ,information, account, and loans, and transaction.


CREDITS CARD TRANSACTION: For purchases on credits cards and generation of monthly statements.

UNIVERSITIES: For students information, course registration, and grades.

AIRLINE: For reservation and schedule information. Airline were among the first to use database in a geographically distributed manner terminals situated around the world accessed the central database system through phone lines and other data network.


PURPOSE OF DBMS

Provides secure and survivable medium for storage & retrieval of data

Data shared among several users & is persistent

Provides mechanism to create, access and manipulate data without compromising security and integrity of data

Redundancy can be reduced Inconsistency can be avoided

CONVENTIONAL FILE PROCESSING SYSTEM VS

DATABASE SYSTEM


o A data can be stored in either CONVENTIONAL FILE PROCESSING SYSTEM or a DATABASE SYSTEM

o In conventional file processing system, each & every subsystem of the information will have its own set of files. As a result, there will be duplication of data between various subsystems.

o But in database systems, there is a single centralized database which minimizes the redundancy of data to a greater extent.


File processing system

• File processing system- stores permanent records in various files, & it needs different application programs to extract records from, and add records to, the appropriate files.


Disadvantages of File processing system

Data redundancy and inconsistencyDifficulty in accessing dataData isolationIntegrity problemsAtomicity problemsConcurrent-access anomalies Security problems


Data redundancy and inconsistency

• Data redundancy - Same information may be duplicated in several places. e.g. Customer Name, NI number, Address is present in several different files on several different systems. Errors are generated, time entering data is wasted, computer resources are needlessly taken up and updates can be an enormous problem.

• Data inconsistency All copies may not be updated properly it will become a problem e.g. information is duplicated in each system and may be updated in most systems but not necessarily in all – the savings account and loan account may have different addresses for a particular customer.


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.


Integrity problems

• Data lacks integrity , i.e. this is the quality by which information from the system can be trusted. The problems already stated show that information can be out of date, can have different values in different parts of the system, can be inaccurate etc.

• 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.


Atomicity problems

• Transfer of funds from one account to another should either complete or not happen at all


Concurrent-access anomalies

• Concurrent accessed needed for performance Uncontrolled concurrent accesses can lead to inconsistencies

• Example: Two people reading a balance and updating it at the same time


Security problems

• Lack of security i.e. there are no restrictions on who can see what.

• 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.


REFERENCE BOOKS:

• 1. DATABASE SYSTEM CONCEPTS (6th edition), by Abraham Silberschatz, Henry F. Kroth & S. Sudarshan, McGRAW-HILL

• 2. DATABASE MANAGEMENT SYSTEM by Seema Kedar, Technical publication


Engineering

DATABASE MANAGEMENT