DBMS Introduction

Objectives:

• To Understand the basic concepts and the applications of database systems
• To Master the basics of SQL and construct queries using SQL
• To understand the relational database design principles
• To become familiar with the basic issues of transaction processing and concurrency control
• To become familiar with database storage structures and access techniques

Introduction to Database Management System

As the name suggests, the database management system consists of two parts. They are:
1. Database and
2. Management System

What is a Database?
To find out what database is, we have to start from data, which is the basic building block of any DBMS.
Data: Facts, figures, statistics etc. 
Record: Collection of related data items, e.g. in the above example the three data items had no meaning. But if we organize them in the following way, then they collectively represent meaningful information

What is Management System?

A database-management system (DBMS) is a collection of interrelated data and a set of programs to access
those data. This is a collection of related data with an implicit meaning and hence is a database. The collection
of data, usually referred to as the database, contains information relevant to an enterprise. The primary goal of
a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient. By
data, we mean known facts that can be recorded and that have implicit meaning.

Database Management System (DBMS) and Its Applications:

A Database management system is a computerized record-keeping system. It is a repository or a container for
collection of computerized data files. The overall purpose of DBMS is to allow he users to define, store, retrieve
and update the information contained in the database on demand. Information can be anything that is of
significance to an individual or organization.
Databases touch all aspects of our lives. Some of the major areas of application are as follows:
1. Banking
2. Airlines
3. Universities
4. Manufacturing and selling
5. Human resources

 

Advantages of DBMS:

Controlling of Redundancy: Data redundancy refers to the duplication of data (i.e storing same data multiple times). In a database system, by having a centralized database and centralized control of data by the DBA the unnecessary duplication of data is avoided. It also eliminates the extra time for processing the large volume of data. It results in saving the storage space.

Improved Data Sharing : DBMS allows a user to share the data in any number of application programs. Data Integrity : Integrity means that the data in the database is accurate. Centralized control of the data helps in permitting the administrator to define integrity constraints to the data in the database. For example: in customer database we can can enforce an integrity that it must accept the customer only from Noida and Meerut city.
Security : Having complete authority over the operational data, enables the DBA in ensuring that the only mean of access to the database is through proper channels. The DBA can define authorization checks to be carried out whenever access to sensitive data is attempted.
Data Consistency : By eliminating data redundancy, we greatly reduce the opportunities for inconsistency. For example: is a customer address is stored only once, we cannot have disagreement on the stored values. Also updating data values is greatly simplified when each value is stored in one place only. Finally, we avoid the wasted storage that results from redundant data storage.
Efficient Data Access : In a database system, the data is managed by the DBMS and all access to the data is through the DBMS providing a key to effective data processing Enforcements of Standards : With the centralized of data, DBA can establish and enforce the data standards which may include the naming conventions, data quality standards etc.
Data Independence : Ina database system, the database management system provides the interface between the application programs and the data. When changes are made to the data representation, the meta data obtained by the DBMS is changed but the DBMS is continues to provide the data to application program in the previously used way. The DBMs handles the task of transformation of data wherever necessary.
Reduced Application Development and Maintenance Time : DBMS supports many important functions that are common to many applications, accessing data stored in the DBMS, which facilitates the quick development of application.

Disadvantages of DBMS
1) It is bit complex. Since it supports multiple functionality to give the user the best, the underlying software has become complex. The designers and developers should have thorough knowledge about the software to get the most out of it.
2) Because of its complexity and functionality, it uses large amount of memory. It also needs large memory to run efficiently.
3) DBMS system works on the centralized system, i.e.; all the users from all over the world access this database. Hence any failure of the DBMS, will impact all the users.
4) DBMS is generalized software, i.e.; it is written work on the entire systems rather specific one. Hence some of the application will run slow.

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