Database System Architecture

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 • 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 • 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.