Database Management System Book 3rd Edition

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What is Database Management System(DBMS) ?

Organizations use large amounts of data. A database management system (DBMS) is a software tool that makes it possible to organize data in a database.

The standard acronym for database management system is DBMS, so you will often see this instead of the full name. The ultimate purpose of a database management system is to store and transform data into information to support making decisions.

A DBMS consists of the following three elements:

The physical database: the collection of files that contain the data
The database engine: the software that makes it possible to access and modify the contents of the database
The database scheme: the specification of the logical structure of the data stored in the database
While it sounds logical to have a DBMS in place, it is worth thinking for a moment about the alternative. What would the data in an organization look like without a DBMS? Consider yourself as the organization for a moment, and the data are all the files on your computer. How is your data organized? If you are like most typical computer users, you have a large number of files, organized in folders.

You may have word processor documents, presentation files, spreadsheets, photographs, etc. You find the information you need based on the folder structure you have created and the names you have given to your files. This is called a file system and is typical for individual computer users.

Now consider the challenges you are faced with. Have you ever lost a file? Have you had difficulty finding a file? Probably. Perhaps you are using multiple computers and your files are located in different physical locations. And, when was the list time you created a backup of all your files? You do back up, right?

You probably get the picture. A file system is relatively simple, but it only works if you keep yourself very organized and disciplined. Now consider an organization with 1,000 employees, each with their own computer. Can you see some of the challenges when using a file system? Do you really want critical financial data floating around the offices as simple files on individual computers?
Functions of a DBMS
So, what does a DBMS really do? It organizes your files to give you more control over your data.

A DBMS makes it possible for users to create, edit and update data in database files. Once created, the DBMS makes it possible to store and retrieve data from those database files.

More specifically, a DBMS provides the following functions:

Concurrency: concurrent access (meaning 'at the same time') to the same database by multiple users
Security: security rules to determine access rights of users
Backup and recovery: processes to back-up the data regularly and recover data if a problem occurs
Integrity: database structure and rules improve the integrity of the data
Data descriptions: a data dictionary provides a description of the data
Within an organization, the development of the database is typically controlled by database administrators (DBAs) and other specialists. This ensures the database structure is efficient and reliable.

Database administrators also control access and security aspects. For example, different people within an organization use databases in different ways. Some employees may simply want to view the data and perform basic analysis. Other employees are actively involved in adding data to the database or updating existing data. This means that the database administrator needs to set the user permissions. You don't want someone who only needs to view the database to accidentally delete parts of the database.

Pros and Cons of DBMS
There are a number of benefits to using a DBMS.

A DBMS provides automated methods to create, store and retrieve data. It may take some time to set up these methods, but once in place, a DBMS can make tedious manual tasks a thing of the past.

A DBMS reduces data redundancy and inconsistency. Have you ever had different versions of the same file on your computer hard drive? The same thing happens in organizations. A well-designed DBMS will eliminate redundancy.


A DBMS allows for concurrent access by multiple users, each with their own specific role. Some users only need to view the data, some contribute to adding new data, while others design and manage the database - all at the same time!

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