1. Department of Computer Science (UG)
Database Management System
(24BCA2T422)
Dr.Poongothai P
Assistant Professor
Department of Computer Science (UG)
Kristu Jayanti College (Autonomous)
Bengaluru.
2. What is a database?
• Database, also called electronic database, any collection of data, or information,
that is specially organized for rapid search and retrieval by a computer.
• Databases are structured to facilitate the storage, retrieval, modification, and
deletion of data in conjunction with various data-processing operations.
• Data base is a collection of related data, i.e known facts that can be recorded and
have implicit meaning.
• Implicit Property of Database
• A database represents some aspect of the real world.
• A database is a logically coherent collection of data with some inherent meaning.
• A database is designed built & populated with data for a specific purpose.
3. What is DBMS (Database Management System)
• DBMS is a collection of programs that enables users to create and maintain the
database.
• It is a general purpose software system that facilitates the process of defining,
constructing & manipulating database for various applications.
• Defining: To specify the data types, structures & constraints of data to be stored
in the database.
• Constructing: To store the data itself on some storage medium that is controlled
by the DBMS.
• Manipulating: Querying the database to retrieve specific data updating the
database to reflect changes in number and generating reports of data.
• Database Management System (DBMS) refers to the technology solution used to
optimize and manage the storage and retrieval of data from databases.
6. DATABASE USERS
• Database users are the one who really use and take the benefits of database. There
will be different types of users depending on their need and way of accessing the
database.
• They can be categorized into:
• 1.Actors on the Scene
• 2.Actors behind the Scene
7. Characteristics of database approach
• There are number of characteristics that distinguish the database approach from the much older
approach of programming with files. In traditional file processing, each user defines and implements
the files needed for a specific software application as part of programming the application.
• For example, one user, the grade reporting office, may keep files on students and their grades.
Programs to print a student’s transcript and to enter new grades are implemented as part of the
application.
• A second user, the accounting office, may keep track of students’ fees and their payments.
• Although both users are interested in data about students, each user maintains separate files— and
programs to manipulate these files—because each requires some data not available from the other
user’s files.
• This redundancy in defining and storing data results in wasted storage space and in redundant efforts
to maintain common up-to-date data.In the database approach, a single repository maintains data that
is defined once and then accessed by various users.
• In file systems, each application is free to name data elements independently. In contrast, in a
database, the names or labels of data are defined once, and used repeatedly by queries, transactions,
and applications.
8. • 1. Potential for Enforcing Standards
• Database applications are meant to reduce the efforts of data management for any organization by
providing well organized and managed data. Such applications will help in faster data processing,
efficient reporting system and quicker decision making.The database approach permits the DBA to
define and enforce standards among database users in a large organization. Standards can be defined
for names and formats of data elements, display formats, report structures and so on.
• When data is shared with the support of DBMS in secure environment it will help DBA and
Developers to define and implement the standards for creation of data elements, defining and storing
data and presentation of data to users. Well defined and well adopted standards make the use of data
easier.
• As DBA it will be easier for you to create database elements like tables, views, procedures, rules,
fieldnames and constraints. Any new employee who replaces an outgoing DBA will not have to
struggle in understanding the data items created by his predecessor. Standards also include how the
data values will be displayed to users, what will be the structure and components of user interface or
screens, what will be a generic format of any report created from the database. For example:
• · Date data must be displayed in dd-mm-yyyy format
• · Names will be displayed as last name, first name and middle name
• · Currency value has to be displayed up to 2 figures after decimal.
Implications of Database Approach
9. • 2. Reduced Application Development Time
• Database approach allows developers to incrementally development the application. Beginning
with core application accepted and approved by users can be enhanced by adding layers of
functionality and complexity demanded by the user who is now well aware of his needs, scope and
capability of application.
• Since the previous versions are well designed, adding new features will be done in lesser time.
The main advantage of database approach is that developing a new application takes a very little
time. Once a database is up and running, less time is required to create new applications using
DBMS facilities.
• 3. Flexibility to alter the data structures
• DBMS allows certain types of changes to the structure of the database without affecting the stored
data and the existing application programs.With time and use of data there may be need to store
data in a different data structures. For example earlier the amount of data was thought to be fit to
store in form of a binary search tree. But with increase in volume of data it is better to store it in an
m-way tree for better search and insertion. Database approach allows this freedom to alter the data
structure with changing requirements of the application or organization.
10. • 4. Availability of up-to-date Information
• A DBMS makes the database available to all users. When one user updates a database, all other users
can immediately see this update. This availability of up-to-date information is essential for
reservation systems, banking databases etc. Data residing at one location and available at different
locations through networked systems is very essential.
• Database approach fulfills this need due to its centralized repository feature. Moreover the data
consistency and real time update implies that the data is readily and quickly available for users going
for on-line reservation like airlines and transactions like banking or online shopping.
• 5. Economy of scalability
• With database approach the organizations can cutoff expenses by minimizing resources and
employees. Data duplicity is considerably reduced so no need to retain copies of data files in multiple
computer systems. Data stored in centralized database server will be available to all the users.
• A person or team devoted for database administration can take care of the information needs across
the organization instead of departmental management of localized data. If the data storage and
management needs increase with time, instead of replacing all the computing resources across
organization only the servers can be upgraded to match the increase in volume of data.Wasteful
overlap of resources and personnel can be avoided by consolidating data and applications across
departments.
11. Advantages of DBMS
• Controlling redundancy:
• In DBMS approach the data required for different users can be stored in a
centralized manner without duplicating the data multiple times. When the data is
stored redundantly several problems like the following arise,
• Duplication of effect as several data has to be entered many times
• Wastage of storage space as the same data is stored many times
• Data may become inconsistent as the updating requires to be done separately on
all files.
12. • Restricting unauthorized access:
• As number of users increases data transferring or data sharing rate also increases thus
increasing the risk of data security. It is widely used in corporation world where
companies invest money, time and effort in large amount to ensure data is secure and is
used properly. A Database Management System (DBMS) provide a better platform for
data privacy and security policies thus, helping companies to improve Data Security.
• When multiple users share the database it is required that the users be authorized and
given certain operation permissions. This is taken care by the authorization and security
subsystem, where the DBA creates accounts and specifies the account restrictions.
• Providing persistent storage for program objects and data structures:
• Database provides persistent storage for program objects and data structures. This is one
of the main reasons for the emergence of object oriented database. The data structures
provided by DBMS are compatible with the programming language data structures.
13. • Representing complex relationships among data:
• DBMS must have the capability to represent a variety of complex relationships among the
data as well as to retrieve and update related data easily & efficiently.
• Providing multiple user interfaces:
• Since person with varying levels of technical knowledge use the database DBMS should
provide a variety of user interface. They include query language for naïve users menu &
natural language interfaces for stand alone users.
• Enforcing integrity constraints:
• DBMS must provide capabilities for defining and enforcing the constraints (rules).
Constraints include specifying the data type, uniqueness of data item etc.
• Providing backup & recovery:
• DBMS must provide facilities for recovering from hardware & software failures. The back
up and recovery subsystem is responsible for recovery.
• Minimized Data Inconsistency:
Data inconsistency occurs between files when different versions of the same data appear
in different places. If a database is properly designed then Data inconsistency can be
greatly reduced hence minimizing data inconsistency.
14. • Better data integration:
Due to Database Management System we have an access to well managed and synchronized form of data thus
it makes data handling very easy and gives integrated view of how a particular organization is working and
also helps to keep a track on how one segment of the company affects other segment.
• Faster data Access:
The Data base management system (DBMS) helps to produce quick answers to database queries thus making
data accessing faster and more accurate. For example, to read or update the data.
• Better decision making:
Due to DBMS now we have Better managed data and Improved data accessing because of which we can
generate better quality information hence on this basis better decisions can be made.
Better Data quality improves accuracy, validity and time it takes to read data.
• Simple:
Data base management system (DBMS) gives simple and clear logical view of data. Many operations like
insertion, deletion or creation of file or data are easy to implement.
15. Disadvantages of DBMS
• Increased costs
• One of the disadvantages of DBMS is database systems require sophisticated hardware, software, and highly skilled personnel.
The cost of maintaining these requisites and managing a database system can be substantial. Training, licensing, and regulation
compliance costs are often unheeded when database systems are employed.
• Management intricacy
• Database systems interface with many different technologies and have a significant impact on a company’s resources and culture.
The changes introduced by the adoption of a database system must be properly managed to ensure that they help advance the
company’s objectives. Given the fact that database systems hold crucial company data that are accessed from multiple sources,
security issues must be assessed constantly.
• Maintaining currency
• To maximize the efficiency of the database system, you must keep your system current. Therefore, you must perform frequent
updates, apply the latest patches, and security measures to all components.As database technology advances rapidly, personnel
training costs tend to be significant. Given the heavy investment in technology and personnel training, companies might be
reluctant to change database vendors.As a consequence, vendors are less likely to offer pricing point advantages to existing
customers, and those customers might be limited in their choice of database system components.
• Frequent upgrade/replacement cycles
• DBMS vendors frequently upgrade their products by adding new functionality. Such new features often come bundled in new
upgrade versions of the software. Some of these versions require hardware upgrades. Not only do the upgrades themselves cost
money, but it also costs money to train database users and administrators to properly use and manage the new features.
16. When not to use DBMS
• In spite of the advantages of using a DBMS, there are a few situations in which a DBMS may involve
unnecessary overhead costs that would not be incurred in traditional file processing.The overhead costs of
using a DBMS are due to the following:
• High initial investment in hardware, software, and training
• The generality that a DBMS provides for defining and processing data
• Overhead for providing security, concurrency control, recovery, and integrity functions
• Therefore, it may be more desirable to use regular files under the following circumstances:
• Simple, well-defined database applications that are not expected to change at all.
• Stringent, real-time requirements for some application programs that may not be met because of DBMS
overhead . Embedded systems with limited storage capacity, where a general-purpose DBMS would not fit.
• No multiple-user access to data
• Certain industries and applications have chosen not to use general-purpose DBMSs. For example, many
computer-aided design (CAD) tools used by mechanical and civil engineers have proprietary file and data
management software that is geared for the internal manipulations of drawings and 3D objects.
• Similarly, communication and switching systems designed by companies like AT&T were early
manifestations of database software that was made to run very fast with hierarchically organized data for
quick access and routing of calls.
• Similarly, GIS implementations often implement their own data organization schemes for efficiently
implementing functions related to processing maps, physical contours, lines, polygons, and so on. General-
purpose DBMSs are inadequate for their purpose.
