INTRODUCTION TO DBMS

           INTRODUCTION 

Database Management System (DBMS) has become the primary mechanism used by most organizations and firms.
A Database Management System (DBMS) is a collection of interconnected data and a set of programs to access those data.  The collection of data is referred to as a database. The primary goal of a DBMS is to provide a way to store the data in an efficient and convenient manner.
Database systems are designed in such a way so that they can store a large amount of data that involves both defining structures and providing a mechanism for the manipulation of information.

DATABASE  SYSTEM  APPLICATIONS

Databases are used widely. Here are some of the applications:

ENTERPRISE INFORMATION-

SALE: For customer and product information. 

ACCOUNTING: For payments, balance, and accounting information. 

HUMAN RESOURCES: For information regarding employees, salaries, taxes, and paychecks.

ONLINE SOURCES: For sales data, online tracking of order, and maintenance of online product evaluations.

BANKING AND FINANCE -

BANKING: For account holder information, loans, and transactions. 
TRANSACTIONS: For the purchase of any product on credit card and generation of monthly statements.
FINANCE: For information about sales and purchase of financial instruments such as stocks; also for online trading by customers. 

TELECOMMUNICATION-

For keeping records of calls made, generating bills, maintaining balance on prepaid calls, and storing information about the connected networks. 

 PURPOSE OF DATABASE SYSTEM

The primary goal of the database management system is to provide a way to store and retrieve database information that is convenient and efficient. Management of data involves both defining structures for storage of information and providing a mechanism for manipulation of information. The database system also ensures the safety of information stored, despite system crashes or attempts at unauthorized access. If data is shared among many users, then the system must avoid possible intimated results. So database system is used to manage large bodies of information and it works on the needs of the particular group. 

Advantages  of Database Management System:

(1) To remove the problem of data redundancy and inconsistency- Data inconsistency means various copies of the same data may no longer agree. For example, a changed customer address may be reflected in saving account records, but not elsewhere in the system.

(2) Easy access of data-Suppose such a program is written and then several days later the same officer needs to trim that list to include only those customers who has an account balance of Rs. 10,000 of more. As expected, a program to generate such a list does not exist; again, the officer has the proceeding two options, neither of which is satisfactory. So without a database management system, data cannot be retrieved conveniently and efficiently.

(3) To solve the data isolation problem- As data are scattered in various files, and files may be in various formats, writing new application programs to retrieve the appropriate data is difficult.

(4) To solve security problems- Not every user of the database system should be able to access all the data. For example in a banking system, payroll personnel needs to see only that part of the database that has information about the various bank employees. They do not need access to information about customer accounts. But, since application programs are added to the systems in an ad- hoc manner, enforcing such security constraints is difficult.

(5) To solve integrity problems- The data values stored in the database must satisfy certain consistency constraints. For example, the balance of a bank account may never fall below a prescribed amount (say $ 25). Developers enforce these constraints in the system by adding if appropriate code in the various applications programs, however when new constraints added, it is difficult to change the program to enforce them. The problem is compound when constraints have involved several data items from different files.

Keeping organizational information in a file processing system has several major disadvantages. 

Advantages  of Database Management System:

(1) Data redundancy is found- the presence of duplicate data in multiple data files e.g. Customer Name, NI number, Address is present in several different files on several different systems. Errors are generated, time entering data is wasted, computer resources are needlessly taken up and updates can be an enormous problem.

(2)Data inconsistency will become a problem- e.g. information is duplicated in each system and may be updated in most systems but not necessarily in all – the savings account and loan account may have different addresses for a particular customer.  

(3) Lack of data independence- (Data dependence refers to the close relationship between data stored in files and the specific software programs needed to update and maintain those files). In the bank imagine cases where any change in data format or structure requires a change in all the programs that access the data. e.g. effort required to change from 3-digit STD to 4-digit STD may be very difficult.

(4) Data lacks integrity- this is the quality by which information from the system can be trusted. The problems already stated show that information can be out of date, can have different values in different parts of the system, can be inaccurate, etc. 

(5) Lack of flexibility-  creating reports, e.g. in this system a summary of account balances in each separate account would require separate reports for each open account or cutting and pasting into a word processor file – not a satisfactory state of affairs. 

These problems among others prompted the development of database systems.