Definition of Database Management System (DBMS) and Components of Database Management System Environment:
Definition Explanation:
Typically database management system is considered as a computerized record
keeping system. However, DBMS is a collection of programs, which are used to
define, create and maintain databases. Basically, DBMS is a general-purpose
software package whose overall purpose" is to create and maintain information
and to make that information available on demand. You can also develop a special
purpose DBMS software (in Visual Basic, C++ etc.) to create and maintain
databases.
There are many functions of general-purpose DBMS software but the main functions
are:
(i) Defining the Structure of Database: which involves defining tables, fields
and their data types, constraints for data to be stored in the database, and the
relationships among tables.
(ii) Populating the Database: which involves storing data into database.
(iii) Manipulating the Database: which involves
to retrieve specific data, update data, delete data, insert new data, and to
generate reports.
Example:
Now consider the example of university computer file processing system as shown
in figure 1.3, which is converted into database management system as shown in
figure 1.7. All of the data about applicants, students, courses, and-faculty is
stored in a single database. The data is integrated into database. It means that
the data items are stored in a compatible format and logical relation among them
is also stored. The database contains a description of its own structure so that
the DBMS "knows" what data items exist and how they are related to each other.
Many users can share the database through the DBMS. The DBMS also provides a
user-interface for online queries. The users can access the database directly
from terminals, using the query language such as SQL statements.
Components of a DBMS Environment
A database management system (DBMS) environment consists of several components.
Each component plays very important role in the DBMS environment. The major
components are:
1. Software
2. Hardware
3. Data
4. Procedures
5. Database Access Language
6. Users
1. Software:
The main component of a DBMS environment is the software. It is a set of
programs used to handle -the databases and to control and manage the overall
computerized database system.
They may include:
- DBMS software, which is the most important software component in the overall system.
- Operating system including network software being used in the network, to
share the data of database among multiple users.
- Application programs developed in programming languages such as C++, Visual
Basic that are used to access database in DBMS environment. Each program
contains statements that request the DBMS to perform different operations on
database. The operations may include retrieving, inserting, updating, deleting
data etc. The application program may be conventional or online the function of
which is to support end-users who are accessing the database from online workstations or terminals. Most of the modern application programs are online, developed by using ASP or JSP technology.
- Others include application development tools, report writers, and so on.
2. Hardware:
Hardware consists of a set of physical electronic devices such as computers
(together with associated I/O devices like disk drives), storage devices, I/O
channels, electromechanical devices that make interface between computers and
the real world systems etc., and so on. It is impossible to implement the DBMS
without the hardware devices. In a network, a powerful computer with very high
data processing speed and a storage device with large storage, capacity is
required as database server,
3. Data:
Data is the most important component of the DBMS environment. In DBMS, databases
are defined, constructed and then data is stored, updated and retrieved to and
from the databases. The database contains both the actual (or operational) data
and the metadata (data about data or description about data).
The data in database is integrated and can be
joined together to generate complicated reports. Data can also be easily shared
among different users. The data integration and data sharing provide the major
advantages of a database system.
- Data Integration means that data in the database is stored in compatible
formats and logical relations among them are also created.
- Data Sharing means that individual pieces of data in the database can be
shared among different users. Each of those users can have access to the same
piece of data at the same time and different users can use it for different
purposes,
4. Procedures:
Procedures refer to the instructions and rules that help to design the database
and to use the DBMS. The users- who operate and manage the DBMS require
documented procedures to use or run the DBMS. These may include.
- Procedure to install the new DBMS.
- To log on to the DBMS.
- To use the DBMS or application program.
- To make, backup copies of the databases.
- To handle hardware and software failures.
- To change the structure of the databases.
- To generate the reports of data retrieved from the databases etc.
5. Database Access Language:
The database access language is used to communicate (or to access) the data to
and from the database. The users use the database access language to enter new
data, change the existing data in database and retrieve required data from
databases. The user writes a set of appropriate commands in a database access
language and submits these to the DBMS. The DBMS translates the user's commands
and sends it to a specific part of the DBMS called the Database Engine. The
database engine generates a set of results according to the commands submitted
by the user, converts these into a user readable form called an Inquiry Report
and then displays them on the screen. The administrators may also use the
database access language to create and maintain the databases.
The most popular database access language is SQL
(Structured Query Language). Relational Databases are required to have a
database query language. Today most of the RDBMSs use the SQL as database access
language.-Ms-Access also uses the SQL to perform different operations on the
databases. are normally hidden from the users.
6. Users:
The users are the people who manage the databases and perform different
operations on the databases in the database system. Figure 1.8 shows different
users that may be involved, in a database management system.
There are three
kinds of people who play different roles in database system. These are:
(i) Application Programmers
(ii) Database Administrators
(iii) End Users
(i) Application Programmers:
The people who write application programs in programming languages (such as
Visual Basic, Java, or C++) to interact with databases are called Application
Programmers. The end-users use the application program written by the
application programmer. The software used in libraries, shopping stores, medical
stores and search engines (on Internet) are examples of application database
programs, The application programmer designs a user-friendly interface of the
program so that the end-users can use the application program very easily.
(ii) Database Administrator:
A person who is responsible for managing the overall database management system
is called database administrator or simply DBA. A database administrator shares
(or performs) the following major responsibilities.
- Installing and managing the DBMS.
- Creating databases and related objects like tables and indexes.
- Authorizing access to the database.
- Coordinating and monitoring DBMS.
- Acquiring software and hardware resources as needed.
- Security and integrity control.
- Maintenance of the operational system.
- Creating backup of data regularly so that if a database is lost or corrupted
due to hardware failure (or any other reason), a copy of the same data is
available to restore the database to its previous state.
(iii) End-Users:
The end-users are the people who interact with DBMS to perform different
operations on database such as retrieving, updating, inserting deleting data
etc. The end-users access the DBMS through application programs interface, IDE
provided by DBMS or SQL interface. The interface is provided as an integral part
of DBMS. Such interfaces are also supported by means of online applications to
interact with online databases from online workstations or terminals.
End-users can be classified into following
categories.
(a) Casual End-Users:
They are also called sophisticated users. These are the trained persons who know
the structure of database and facilities offered by the DBMS. They use the
standard query language such as SQL to perform the required operations on the
database. They access the databases by entering queries. Some sophisticated
end-users may even write application programs for their own use.
(b) Naive Users:
They do not know the structure of database or any query language. They have no
technical knowledge about the DBMS. They access the database through application
programs (or IDE) that have been written for them. They access the data by
selecting options from menus or by entering simple commands. For example, in the
registrar's office, a clerk may be a naive user, while the registrar's data
entry operator may be a casual user.
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