Database Systems

Three Schema architecture

Dbms components

Client server architecture

DBMS vs File System: DBMS eliminates data redundancy, ensures data integrity, security, supports multiple users, backup & recovery, and efficient query processing, whereas file systems lack these features.

Three-Schema Architecture: Comprises External (user views), Conceptual (community user view), and Internal (physical storage) levels with mappings ensuring data abstraction and independence.

Data Independence: Logical independence allows changes in conceptual schema without affecting external views (harder to achieve); Physical independence allows changes in physical schema without impacting conceptual schema.

DBA Role: Responsible for database setup, maintenance, security, backup/recovery, and query optimization knowledge even if not writing queries themselves.

DBMS Components: Key modules include DDL compiler (processes schema definitions), DML compiler (processes data manipulation statements), Query compiler (analyzes and optimizes queries), Runtime processor (executes operations), and Stored Data Manager (handles storage).

Real-World Design: DBMS architecture applied in systems like ticket booking and online course platforms using data abstraction and ensuring security, concurrency, and integrity.

Schema vs State: Schema defines database structure; State represents current data in the database instance.

User Types: Naive users, Application programmers, Sophisticated users (advanced querying), and DBAs, each interacting differently with the DBMS.