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A DBMS is a software that allows creation, definition and manipulation of database, allowing users to store, process and analyse data easily. DBMS provides us with an interface or a tool, to perform various operations like creating database, storing data in it, updating data, creating tables in the database and a lot more.

DBMS also provides protection and security to the databases. It also maintains data consistency in case of multiple users.

Many types of database management systems are available in the market nowadays. One can purchase license of any database from its vendor and start using it. Also, there are some open source database management systems for which there is no license required to use it. It is available on the Internet. One can download it and use it. The source code is also available for free which could be modified by any user and redistributed. MySQL is one of the most popular open source database management system

Here are some examples of popular DBMS used these days:

• MySql
• Oracle
• SQL Server
• IBM DB2
• PostgreSQL
• Amazon SimpleDB (cloud based) etc.

Below table contains some examples of database management system and the vendor company who provides it.

Database Management System	Vendor (Supplier)
Oracle	Oracle
SQL Server	Microsoft
Access	Microsoft
DB2	IBM

Advantages of DBMS

• Segregation of applicaion program.
• Minimal data duplicacy or data redundancy.
• Easy retrieval of data using the Query Language.
• Reduced development time and maintainance need.
• With Cloud Datacenters, we now have Database Management Systems capable of storing almost infinite data.
• Seamless integration into the application programming languages which makes it very easier to add a database to almost any application or website.

Disadvantages of DBMS

• It's Complex system
• Except MySQL, which is open source, licensed DBMSs are generally costly.
• They are large in size.

What is a database state? What are the various states of the database?

Ans: The data in the database at a particular point of time are known as database instance or database state or snapshot. The database state is also called an extension of the schema. The various states of the database are:

Empty state: When a new database is defined, only its schema is specified. At this point, the database is said to be in an empty state as it contains no data.

Initial state: When the database is loaded with data for the first time, it is said to be in an initial state.

Current state: The data in the database are updated frequently. Thus, at any point of time, the database is said to be in the current state.

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