Database Management System (DBMS)

A Database Management System (DBMS) is software that lets users create, store, organise, retrieve, update and manage the data in a database. It sits between the user (or an application program) and the actual data stored on the disk, and it takes care of all the low-level details of how the data are physically kept. The user simply asks the DBMS for what they want — 'show all customers from Pune', 'add a new product', 'change this price' — and the DBMS carries out the request safely and efficiently.

A DBMS performs several important functions:

• Data definition — it lets you define the structure of the data: what tables exist, what columns each table has, and what type of data each column holds.
• Data storage and retrieval — it stores the data on disk and fetches exactly the records you ask for, without you needing to know where or how they are physically stored.
• Data manipulation — it lets you insert new data, update existing data, and delete data that is no longer needed.
• Data security — it controls who is allowed to see or change which data, using user names, passwords and permissions.
• Data integrity — it enforces rules so that only valid, consistent data is stored (for example, that a marks column cannot hold a negative value, or that every order must belong to a real customer).
• Backup and recovery — it helps protect data against loss by supporting backups and restoring the database to a correct state after a failure.
• Concurrent access control — it allows many users to work with the same database at the same time without their changes clashing or corrupting each other. …