The architecture of the Database system is described in detail with a neat block diagram and each components explained.

1. DATABASE SYSTEM ARCHITECTURE
Prepared by,
Mr. K.Vignesh Saravanan
Assistant Professor
Department of Computer Science and Engineering
Ramco Institute of Technology
Rajapalayam

2. Centralized DBMS
– The application
program + user
interface + control of
DBMS (data server) in a
single machine
– Access through the
single machine – very
slow computations, lack
of concurrency

3. Two tier architecture
– Client-server architecture
– Client – machine used by end-user.
– Server – high end machine holds
software and hardware
– The application programs run on the
client side
– Client will send Query / request
transaction through ODBC / JDBC

4. Three tier architecture
– Client machine just acts as a front
end and does not contain any
direct database calls
– client end communicates with an
application server
– application server in turn
communicates with a database
system to access Data
– applications that run on the
World Wide Web

5. Database System
Structure
– Database Users and Administrators
– Transaction Management
– Data Storage Manager
– Query Processor

6. Database Users and Administrator
• Naive users are unsophisticated users
• who interact with the system by invoking
• one of the application programs
• Application programmers are computer
• Professionals who write application programs
• Sophisticated users interact with the system
• using tools such as data analysis software
• Database Administrator(DBA) - Schema
definition, modification, Grant/revoke access,
Maintenance.

7. Storage Manager
• Storage requires huge amount of data (largest database)
• Interface between internal Disk and application program and queries submitted
to the system
• Responsible for storing, retrieving and updating data in the database
• Authorization and integrity manager – checks integrity constraints and checks
the authority of users to access data.
• Transaction manager - ensures that the database remains in a
consistent(correctness) all the times.
• File manager - manages the allocation of space on disk storage and the data
structures used to represent information stored on disk.
• Memory(Buffer) manager - which is responsible for fetching data from disk
storage into main memory, and deciding what data to cache in main memory.

8. Disk Storage
• Storage manager interacts with several data structures at physical level (Disk
storage)
– Data files, which store the database itself.
– Data dictionary, which stores metadata about the structure of the database.
– Indices, which can provide fast access to data items. Like the index in this
textbook, a database index provides pointers to those data items that hold a
particular value.

9. Query Processor
• The query processor components include:
DDL interpreter - which interprets DDL statements and records the definitions in
the data dictionary.
DML compiler - which translates DML statements in a query language into an
evaluation plan consisting of low-level instructions that the query evaluation engine
understands.
Query evaluation engine, which executes low-level instructions generated by the
DML compiler.

10. Transaction Management
• A transaction is a collection of operations that handles
transaction in the database by ensuring the properties:
• Atomicity - all-or-none
• Consistency – correctness of data
• Durability – persistence (data should be present)
• Failure recovery – recover from system crash