DATABASE MANAGEMENT SYSTEM (DBMS)

NEED FOR DBMS?

A Database is an organised, persistent collection of data of an organisation.

· The File Based System.

File based system are an early attempt to computerize the manual filling system. For example, a manual file can be set up to hold all the correspondence relating to a particular matter as a project, product, task, client or employee.

The manual filing system works well when the number of items to be stored is small.

· The Database Approach.

A database is a persistent collection of logically related data.

A DBMS controls access to this data and thus needs to provide feature for database creation, data manipulation such as data value modification, data retrieval, data integrity and security etc.

Advantage.

1. Reduction of redundancies

2. Shared data

3. Data independence

4. Improved Integrity

5. Efficient data access

6. Improved Security

7. Improved backup and recovery

THE DBMS ARCHITECTURE

There are two types of DBMS architecture

1. The logical architecture

2. The physical architecture

The Logical architecture

The logical architecture are also knows as three level architecture of DBMS. Its divide the system into three levels of abstraction: The internal or physical level, the conceptual level and the external levels

1. Support of multiple user view

2. Insulation between user programs and data that does not concern them(the user does not deal with direct physical storage.)

The physical architecture

The physical architecture describes the software components used to enter and process data, and how these software components are related and interconnected.

DATABASE MANAGEMENT SYSTEM (languages)

Two basic sets of language

1. DML PRECOMPILER

2. DDL COMPILER

DML PRECOMPILER:-

The DML precompiler converts DML statements embedded in an application program to normal procedural call in the host language.

DDL COMPILER:-

The DDL compiler converts the data definition statements into a set of tables containing metadata tables.

………………………………………………………………

1. FILE MANAGER:-

The file manager manages the allocation of space on disk storage. The file manager does not directly manage the physical output and input of data.

2. DATABASE MANAGER:-

A database manager is a program module responsible for interfacing with the database file system to the user queries.

COMPONENTS

1. AUTHORIZATION CONTROL

2. COMMAND PROCESSOR

3. INTEGRITY CHECKER

4. QUERY OPTIMIZER

5. TRANSACTION MANAGER

6. SCHEDULER

7. RECOVERY MANAGER

8. BUFFER MANAGER

DATABASE ADMINISTRATOR

The DBA is responsible for granting permission to the users of the database and stores the profile of each user in the database. This profile describes the permissible activities of a user on that portion of the database accessible to the user via one or more user views. The user profile can be used by the database system to verify that a particular user can perform a given operation on the database.