Database management system1

DATABASE
MANAGEMENT SYSTEM

DBMS
PREPARED BY:

RAJNEESH SHARMA (310-MBA-08)
RAKESH SINGH JAMWAL (322-MBA-08)

CONTENTS:

• DEFINATION
• ADVANTAGES
• DISADVANTAGES
• THREE LEVEL OF ARCHITECTURE
– EXTERNAL VIEW
– CONCEPTUAL VIEW
– INTERNAL VIEW

DBMS

• DATA: Data is raw fact or figures or
entity.
• DATABASE: A database is an organized
collection of facts. In other words we can
say that it is collection of information
arranged and presented to serve to a
particular purpose.

Database Management
System:
Database management system (DBMS) is a
software system that allows access to data
contained in a database. The objective of
the DBMS is to provide a convenient
effective method of defining, storing and
retrieving the information contained in a
database.

ADVANTAGES:

• Reduction of Redundancies:
Centralized control of data by 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 large mass of data.

• Shared Data:
DBMS allows sharing of data under its control
by any number of application programs or
users.
• Security:
Different level of security could be
implemented for various types of data and
operation. The DBA who has the ultimate
responsibility for the data in the DBMS can
ensure that the proper access procedures
are followed.

• Integrity:
Centralized control can also ensure that
adequate checks are incorporated in the
DBMS to provide data integrity. Data
integrity means that the data contained in
the database is both accurate and
consistent.

DISADVANTAGES:
• A significant disadvantage of the DBMS is
cost. In addition to the cost of purchasing
or developing the software, the hardware
has to be upgraded to allow for the
extensive programs and the work spaces
required for their execution and storage.
• The processing overhead introduced by
the DBMS to implement security, integrity
and sharing of the data causes a
degradation of the response and
throughput time.

• While centralization reduces duplication,
the lack of duplication requires that the
database be adequately backed up , so
that in the case of failure, the data can be
recovered. Backup and Recovery
operations are fairly complex in a DBMS
environment.

THREE LEVEL
ARCHITECTURES
• DBMS provide user with an abstract view
data i.e the system has certain details of
how the data store and maintain.
In DBMS, the data abstracted in three
levels corresponding to three views are
as:
– External View
– Conceptual View
– Internal View

EXTERNAL VIEW
This is the highest level of database
abstraction as seen by the user where
only those portions of the database of
concern to a user or application program
are included. Any number of user views
may exist for a given global or conceptual
view.

CONCEPTUAL VIEW
At this level of database abstraction all the
database entities and the relationship
among them are included. One conceptual
view can represents the entire database.
It describes all the logical records and
relationships in the conceptual view.

INTERNAL VIEW
This view is the lowest level of abstraction,
closest to the physical storage method
used. It indicates how the data stored and
describes the data structures and access
methods to be used by the database.

Database management system1

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