Page 12 - DCAP402_DCAO204_DATABASE MANAGEMENT SYSTEM_MANAGING DATABASE

Unit 1: Database Fundamentals

3. Views: A database may have many users and each one may be interested on a particular Notes
view of the application. A view is conceptually a table, but the records of this table are not
stored in the database.

Example: Consider the Student database in which we can think of two views:

View 1: Students Grade in various courses. To obtain this information the tables Course
and Grade_Report are to be joined and created as a view.
View 2: If we want to know the Prerequisite Courses that a student needs to study, three
tables are to be joined. These tables are nothing but Student, Section and Prerequisite.
4. Sharing and Transaction processing: A DBMS must provide control for various users
trying to access the database.

Example: Railway Reservation System with multiple counters.
Whenever several users try to access the same application at the same time, we call this
situation as concurrent transaction processing. Generally, the concurrent access is achieved
with a simple Local Area Network (LAN). It is also possible to book railway tickets online
i.e. through Internet.

1.4 Advantages of DBMS

One of the main advantages of using a database management system is that the organization can
exert via the DBA, centralized management and control over the data. The database administrator
is the focus of the centralized control. If any application requiring a change in the structure of a
data record, the DBA makes the necessary modifications, which do not affect other applications
or users of the record in question.

The following are the major advantages of using a Database Management System (DBMS):
1. Reduction of Redundancies: Centralized control of data by the DBA avoids unnecessary
duplication of data and effectively reduces the total amount of data storage required. It
also eliminates the extra processing necessary to trace the required data in a large mass of
data. Another advantage of avoiding duplication is the elimination of the inconsistencies
that tend to be present in redundant data files.
2. Data Independence and Efficient Access: Database application programs are independent
of the details of auto representation and storage. In addition a DBMS provides efficient
storage and retrieval mechanisms, including support for very large files, index structures
and query optimization.
3. Data Integrity: Centralized control can also ensure that adequate checks are incorporated
in the DBMS to provide data integrity, which means that the data contained in the database
is both accurate and consistent. Therefore, data values being entered for storage could be
checked to ensure that they fall within a specified range and are of the correct format. For
example, the value for the age of an employee may be in the range of 16 and 75. Also it
should be ensured that if there is a reference to certain object, that object must exist. In the
case of an automatic teller machine, for example a user is not allowed to transfer funds
from a nonexistent savings account to a checking account.

4. Data Security: Confidential data must not be accessed by unauthorized persons. Different
levels of security could be implemented for various types of data and operations.

LOVELY PROFESSIONAL UNIVERSITY 5