8/9/2019 Experiment No. 1 (1)-(f)

1/6

EXPERIMENT NO. 1

AIM: Introduction to DBMS and RDBMS

Database Management System (DBMS)

A Database Management System is a set ofcomputer programs that controls the creation,

maintenance, and the use of the database with computer as a platform or of an

organization and its end users. It allows organizations to place control of organization-

wide database development in the hands of database administrators (DBAs) and other

specialists. A DBMS is a system software package that helps the use of integrated

collection of data records and files known as databases. It allows different user

application programs to easily access the same database. DBMSs may use any of a

variety of database models, such as the network model or relational model. In large

systems, a DBMS allows users and other software to store and retrieve data in a

structured way. Instead of having to write computer programs to extract information, user

can ask simple questions in a query language.

The DBMS accepts requests for data from an application program and instructs the

operating system to transfer the appropriate data. The queries and responses must besubmitted and received according to a format that conforms to one or more applicable

protocols. When a DBMS is used, information systems can be changed much more easily

as the organization's information requirements change. New categories of data can be

added to the database without disruption to the existing system.

Advantages

Flexibility : Because programs and data are independent, programs do not have to

be modified when types of unrelated data are added to or deleted from the

database, or whenphysical

storage changes.

Fast Response to Information Requests : Because data are integrated into a

single database, complex requests can be handled much more rapidly then if the

data located in separate, non-integrated files.

http://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/End_userhttp://en.wikipedia.org/wiki/Database_administratorhttp://en.wikipedia.org/wiki/Database_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Relational_modelhttp://en.wikipedia.org/wiki/Data_structurehttp://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Querieshttp://en.wikipedia.org/wiki/Information_systemhttp://www.blurtit.com/q955157.htmlhttp://www.blurtit.com/q955157.htmlhttp://en.wikipedia.org/wiki/Computer_programhttp://en.wikipedia.org/wiki/Databasehttp://en.wikipedia.org/wiki/End_userhttp://en.wikipedia.org/wiki/Database_administratorhttp://en.wikipedia.org/wiki/Database_modelhttp://en.wikipedia.org/wiki/Network_modelhttp://en.wikipedia.org/wiki/Relational_modelhttp://en.wikipedia.org/wiki/Data_structurehttp://en.wikipedia.org/wiki/Query_languagehttp://en.wikipedia.org/wiki/Operating_systemhttp://en.wikipedia.org/wiki/Querieshttp://en.wikipedia.org/wiki/Information_systemhttp://www.blurtit.com/q955157.htmlhttp://www.blurtit.com/q955157.html

8/9/2019 Experiment No. 1 (1)-(f)

2/6

Multiple Access : Database software allows data to be accessed in a variety ofways and often, by using several programming languages.

Lower User Training Costs : Users often find it easier to learn such systems and

training costs may be reduced. Also, the total time taken to process requests may

be shorter, which would increase user productivity.

Less Storage : Theoretically, all occurrences of data items need be stored only

once, thereby eliminating the storage of redundant data. System developers and

database designers often use data normalization to minimize data redundancy.

Systematic Storage : The data is stored in the form of tables. The tables consists

of rows and columns. The primary and secondary key help to eliminate data

redundancy, enabling systematic storage of data.

Data Security : Data is the most important asset. Therefore, there is a need for

data security. Database management systems help to keep the data secured.

Multiple Simultaneous Usages : The database can be used simultaneously by a

number of users. Various users can retrieve the same data simultaneously.

Privileges : Different privileges can be given to different users. For example,

some users can edit the database, but are not allowed to delete the contents of the

database.

Data Consistency : Data consistency ensures a consistent view of data to every

user. It includes the accuracy, validity and integrity of related data. The data in the

database must satisfy certain consistency constraints, for example, the age of a

candidate appearing for an exam should be of number data type and in the range

http://www.blurtit.com/q955157.htmlhttp://www.blurtit.com/q955157.html

8/9/2019 Experiment No. 1 (1)-(f)

3/6

of 20-25. When the database is updated, these constraints are checked by the

database systems.

Abstract View of Data and Easy Retrieval : DBMS enables easy and convenient

retrieval of data. A database user can view only the abstract form of data; the

complexities of the internal structure of the database are hidden from him. The

data fetched is in user friendly format.

Disadvantages

Cost of Hardware & Software : Aprocessorwith high speed of data processing

and memory of large size is required to run the DBMS software. It means that you

have to up grade the hardware used for file-based system. Similarly, DBMS

software is also very costly.

Cost of Data Conversion : When a computer file-based system is replaced with a

database system, the data stored into data file must be converted to database file.

It is very difficult and costly method to convert data of data files into database.

You have to hire database and system designers along with application

programmers. Alternatively, you have to take the services of some software

house. So a lot ofmoneyhas to be paid for developing software.

Cost of Staff Trailing : Most DBMSs are often complex systems so the training

for users to use the DBMS is required. Training is required at all levels, including

programming, application development and database administration. Theorganization has to be paid a lot of amount for the training of staff to run the

DBMS.

Appointing Technical Staff : The trained technical persons such as database

administrator, application programmers, data entry operators etc. are required to

handle the DBMS. You have to pay handsome salaries to these persons.

Therefore, the system cost increases.

http://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.htmlhttp://www.blurtit.com/q217827.html

8/9/2019 Experiment No. 1 (1)-(f)

4/6

Database Damage : In most of the organizations, all data is integrated into a

single database. If database is damaged due to electric failure or database is

corrupted on the storage media, then your valuable data may be lost forever.

Lower Efficiency : A database system is a multi-use software which is often less

efficient than specialised software which is produced and optimised exactly for

one problem.

As users can access the data from any place, any time so some techniques are

needed to control quality of data. Several users can access data directly, so many

opportunities for users exist to damage data.

Relational Database Management System (RDBMS)

One of the most popularly used database models is the relational model. It was developed

by Edgar Codd in 1969. This model provides a declarative method for specification of

data and queries. In a relational model of a database, the database users directly state the

information they want to be retrieved from it and abstract away from the responsibility of

describing the data structures that are used to store data. A database that confirms to the

relational database model is known as a relational database.

A relational database is a collection of relations or tables. The rows of a table in a

relational database are known as tuples and each column of a table is called an attribute.

By definition, a relation becomes a set of tuples having the same attributes. Operations,

which can be performed on the relations are select, project and join. The join operation

combines relations, the select queries are used for data retrieval and the project operation

identifies attributes. Similar to other database models, even relational databases support

the insert, delete and update operations.

Advantages

Relational databases are based on relational set theory. A relational database

supports relational algebra, consequently supporting the relational operations of

the set theory. Apart from mathematical set operations namely, union,

intersection, difference and Cartesian product, relational databases also support

8/9/2019 Experiment No. 1 (1)-(f)

5/6

select, project, relational join and division operations. These operations are unique

to relational databases.

Relational databases support an important concept of dynamic views. In a

relational database, a view is not a part of the physical schema, it is dynamic.

Hence changing the data in a table alters the data depicted by the view. Views can

subset data, join and simplify multiple relations, dynamically hide the complexity

in the data and reduce the data storage requirements.

Relational databases use SQL, which is an easy and human-readable language .

SQL instructions are in the form of plain instructions, which can be put to the

database for implementation. Relational databases provide the users with simple

operations to manipulate data in the databases and retrieve it. Moreover relational

databases establish defined relationships between the tables, thus giving their

users a complete picture of the data stored.

Relational databases have an excellent security. A relational database supports

access permissions, which allow the database administrator to implement need-

based permissions to the access of the data in database tables. Relational

databases support the concept of users and user rights, thus meeting the security

needs of databases.

The other important advantages of relational databases include their

performance, power, and support to new hardware technologies as also

flexibility and a capacity to meet all types of data needs. Relational databases are

scalable and provide support for the implementation of distributed systems.

Disadvantages

Cost: One disadvantage of relational databases is the expensive of setting up and

maintaining the database system. In order to set up a relational database, you

generally need to purchase special software. It does take time to enter in all the

information and set up the program.

8/9/2019 Experiment No. 1 (1)-(f)

6/6

If your company is large and you need a more robust database, you will need to

hire a programmer to create a relational database using Structured Query

Language (SQL) and a database administrator to maintain the database once it is

built.

Abundance of Information: Advances in the complexity of information cause another

drawback to relational databases. Relational databases are made for organizing data

by common characteristics. Complex images, numbers, designs and multimedia

products defy easy categorization.

Structured Limits: Some relational databases have limits on field lengths. When you

design the database, you have to specify the amount of data you can fit into a field.

Some names or search queries are shorter than the actual, and this can lead to data

loss.

Isolated Databases: Complex relational database systems can lead to these databases

becoming "islands of information" where the information cannot be shared easily

from one large system to another. Often, with big firms or institutions, you find

relational databases grew in separate divisions differently.