Basic Concepts-DataBase Management Systems

It is a collection of information. The facts that can be recorded and which have implicit meaning known as ‘data’.
Example: Customer

It is a collection of interrelated data.
These can be stored in the form of tables.
A database can be of any size and varying complexity.
A database may be generated and manipulated manually or it may be computerized.
Customer database consists the fields as cname, cno, and ccity



Database System:
It is computerized system, whose overall purpose is to maintain the information and to make that the
information is available on demand.
1.Redundency can be reduced.
2.Inconsistency can be avoided.
3.Data can be shared.
4.Standards can be enforced.
5.Security restrictions can be applied.
6.Integrity can be maintained.
7.Data gathering can be possible.
8.Requirements can be balanced.

Database Management System (DBMS):
It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose
software that provides the users with the processes of defining, constructing and manipulating the database for
various applications.
Disadvantages in File Processing
Data redundancy and inconsistency.
Difficult in accessing data.
Data isolation.
Data integrity.
Concurrent access is not possible.
Security Problems.

Advantages of DBMS:
1.Data Independence.
2.Efficient Data Access.
3.Data Integrity and security.
4.Data administration.
5.Concurrent access and Crash recovery.
6.Reduced Application Development Time.

Database Applications:
Banking: all transactions
Airlines: reservations, schedules
Universities: registration, grades
Sales: customers, products, purchases
Online retailers: order tracking, customized recommendations
Manufacturing: production, inventory, orders, supply chain
Human resources: employee records, salaries, tax deductions

People who deal with databases
Many persons are involved in the design, use and maintenance of any database. These persons can be
classified into 2 types as below.
Actors on the scene:
The people, whose jobs involve the day-to-day use of a database are called as ‘Actors on the scene’,
listed as below.

1.Database Administrators (DBA):
The DBA is responsible for authorizing access to the database, for
Coordinating and monitoring its use and for acquiring software and hardware resources as needed.
These are the people, who maintain and design the database daily.
DBA is responsible for the following issues.
a. Design of the conceptual and physical schemas:
The DBA is responsible for interacting with the users of the system to understand what data is to
be stored in the DBMS and how it is likely to be used.
The DBA creates the original schema by writing a set of definitions and is
Permanently stored in the ‘Data Dictionary’.
b. Security and Authorization:
The DBA is responsible for ensuring the unauthorized data access is not permitted.
The granting of different types of authorization allows the DBA to regulate which parts of the
database various users can access.
c. Storage structure and Access method definition:
The DBA creates appropriate storage structures and access methods
by writing a set of definitions, which are translated by the DDL compiler.
d. Data Availability and Recovery from Failures:
The DBA must take steps to ensure that if the system fails, users can continue to access as much
of the uncorrupted data as possible.
The DBA also work to restore the data to consistent state.
e. Database Tuning:
The DBA is responsible for modifying the database to ensure adequate
Performance as requirements change.
f. Integrity Constraint Specification:
The integrity constraints are kept in a special system structure that is consulted by the DBA
whenever an update takes place in the system

2.Database Designers:
Database designers are responsible for identifying the data to be stored in the database and for choosing appropriate
structures to represent and store this data.

3. End Users:
People who wish to store and use data in a database.
End users are the people whose jobs require access to the database for querying, updating and generating reports,
listed as below.
a. Casual End users:
These people occasionally access the database, but they may need different information each
b. Naive or Parametric End Users:
Their job function revolves around constantly querying and updating the database using
standard types of queries and updates.
c. Sophisticated End Users:
These include Engineers, Scientists, Business analyst and others familiarize to implement their
applications to meet their complex requirements.
d. Stand alone End users:
These people maintain personal databases by using ready-made program packages that provide
easy to use menu based interfaces.

4.System Analyst:

These people determine the requirements of end users and develop specifications for transactions.

5.Application Programmers (Software Engineers):
These people can test, debug, document and maintain the specified transactions.

b. Workers behind the scene:
Database Designers and Implementers:
These people who design and implement the DBMS modules and interfaces as a software package.

2.Tool Developers:

Include persons who design and implement tools consisting the packages for design, performance monitoring,
and prototyping and test data generation.

3.Operators and maintenance personnel:
These re the system administration personnel who are responsible for the actual running and maintenance of the
hardware and software environment for the database system.

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