Database System Architecture
A Database Management System is not just about storing data; it follows a well-defined internal structure to ensure efficiency, security, and consistency. This internal structure is known as Database System Architecture. It explains how data is stored, accessed, and managed inside a DBMS.
What is Database System Architecture?
Database System Architecture refers to the logical design of a DBMS that defines how users interact with the database, how data is processed, and how it is physically stored. It separates the user view from the physical storage of data, making database management easier and more flexible.
Objectives of Database Architecture
The main goals of database architecture are:
- To provide data abstraction
- To ensure data independence
- To improve security and integrity
- To allow efficient data access
- To support multiple users simultaneously
Levels of Database Architecture
DBMS architecture is mainly divided into three levels:
1. External Level (View Level)
The external level represents the user’s view of the database.
Each user sees only the data that is relevant to them.
Features:
- Different users have different views
- Provides data security
- Hides irrelevant data
Example:
A student sees only their marks, while an admin sees the complete database.
2. Conceptual Level (Logical Level)
The conceptual level describes what data is stored and the relationships among the data.
Features:
- Defines tables, attributes, relationships
- Independent of physical storage
- Managed by the database administrator
This level acts as a bridge between the external and internal levels.
3. Internal Level (Physical Level)
The internal level defines how data is physically stored on storage devices.
Features:
- Data storage format
- Indexing techniques
- File structures
- Disk allocation
Users never directly interact with this level.
Schema and Mapping
A schema is a blueprint of the database structure.
Types of schemas:
- External schema
- Conceptual schema
- Internal schema
Mapping is used to convert requests from one level to another, ensuring smooth data access.
Data Independence
One of the biggest advantages of DBMS architecture is data independence.
Types:
- Logical Data Independence – Changes in logical structure do not affect user views
- Physical Data Independence – Changes in physical storage do not affect logical structure
Components Involved in DBMS Architecture
A database system includes:
- Query Processor
- Storage Manager
- Database Engine
- Transaction Manager
- Authorization and Integrity Manager
These components work together to process queries and maintain data consistency.
Advantages of Three-Level Architecture
- Improved data security
- Easy database maintenance
- Reduced application development time
- Flexibility in database design
- Better performance and scalability
Conclusion
Database System Architecture provides a structured way to design and manage databases efficiently. The three-level architecture ensures data abstraction, security, and independence, making DBMS suitable for complex and large-scale applications. Understanding this architecture is essential for building reliable database systems.