Introduction

Database Management System is a software that allows access to data stored in a database and provides an easy and effective method of

• Defining the information.
• Storing the information.
• Manipulating the information.
• Protecting the information from system crashes or data theft.
• Differentiating access permissions for different users.

Structure Of DBMS

1.QueryProcessor

• It interprets the requests received from end user via an application program into instructions.
• It also executes the user request which is received from the DML compiler.

Embedded DML Pre-compiler

It processes DML statements embedded in an application program into procedural calls.

Query Optimizer

• It executes the instruction generated by DML Compiler.
• It executes the DCL statements.
• It is responsible for updating, storing, deleting, and retrieving data in the database.

2. Storage Manager

• Storage Manager is a program that provides an interface between the data stored in the database and the queries received.
• It is also known as Database Control System.

Authorization Manager

It ensures role-based access control, i.e,. checks whether the particular person is privileged to perform the requested operation or not.

Integrity Manager

It checks the integrity constraints when the database is modified.

File Manager

It manages the file space and the data structure used to represent information in the database.

Buffer Manager

It is responsible for cache memory and the transfer of data between the secondary storage and main memory.

3. Disk Storage

Data Files

It stores the data.

Data Dictionary - It contains the information about the structure of any database object. - It is the repository of information that governs the metadata.

Indices

It provides faster retrieval of data item.