1. Database System Architecture

3. The Functional Components of a database system can be divided into 3 units
Storage Manager
Query Processor
Database users and administrators.

4. Storage Manager
It is a program module that provides an interface between the database and application program.
The storage manager is responsible for storing, retrieving and updating the data in the database.

5. Storage Manager Components
Authorization and Integrity manager
Which tests for the satisfaction of integrity constraints and checks the authority of users to access data.
Transaction Manager
Which ensures that the database remains in a consistent state when the system failures and that concurrent transaction executions proceed without conflicting.

6. Storage Manager Components
File Manager
Which manages the allocation of storage space on disk and data structures used to store those information's
Buffer Manager
Which is responsible for fetching data from disk into main memory.

7. Data Structure used by the storage Manager
Data Files
Stores database
Data dictionary
Structure of the database
Indices
Which can provide fast access to data items. Hashing technique is used for accessing

8. Query Processor DDL Interpreter DML Compiler Query Evaluation Engine
Which interprets DDL statements (Convert DDL statement into Low level data)
DML Compiler
Translates MDML statements
Query Evaluation Engine
Which execute low level instructions generated by the DML compiler.

9. Database Users Application programmers Sophisticated users
Program written in a host language
Sophisticated users
Interact with the database using query language (analysis)
Specialized user
Specialized users who write specialized database applications that do the into the traditional data processing frame work (example CAD system, Knowledge based expert system)
Naïve users
Interact with the system by invoking one of the permanent application (tellers agents, web users)

10. Database Administrator
A Person who has such central control over the system is called a database administrator (DBA).
The functions are
Schema definition
Set of data definition statements in the DDL.
Storage structure and access method definition
Schema and physical organization modification.
Alter the physical organization to improve performance
Granting of authorization for data access (give authorization)
Routine maintenance
Periodically backup database
Ensuring that enough free disk space
Monitoring jobs

11. DBMS

12. Advantages of DBMS Control of data redundancy Data Consistency
Sharing of data
Improved security
Enforcement of standards
Economy of scale
Balance of conflicting requirements
Improved data accessibility and responsiveness.
Increased productivity
Increased maintenance through data independence.
Increased concurrency.
Improved backup and recovery services.

13. Disadvantages of DBMS Complexity Size Cost of DBMS
Additional hardware cost
Cost of conversion
Performance
Higher impact of failure.