1. Database system architecture can be divided into 1-tier, 2-tier, or 3-tier. 3-tier is most widely used and separates components based on user complexity and data use. 2. A database system has three main components - storage manager, query processor, and database users/administrators. The storage manager stores, retrieves, and updates data using various sub-components. 3. The query processor interprets queries and evaluates them against the database. Database users include programmers, analysts, specialized application users, and basic users. The database administrator controls the system and ensures security, backups, and performance.

1. DATABASE SYSTEM
ARCHITECTURE

2. 1-Tier Architecture
• In 1-tier architecture, the DBMS is the only entity where
the user directly sits on the DBMS and uses it.
• Any changes done here will directly be done on the
DBMS itself. It does not provide handy tools for end-
users.
• Database designers and programmers normally prefer

4. 2-Tier Architecture
• If the architecture of DBMS is 2-tier, then it must have an
application through which the DBMS can be accessed.
• Programmers use 2-tier architecture where they access
the DBMS by means of an application.
• Here the application tier is entirely independent of the
database in terms of operation, design, and
programming.

6. 3-Tier Architecture
• A 3-tier architecture separates its tiers from each
other based on the complexity of the users and
how they use the data present in the database.
• It is the most widely used architecture to design a
DBMS.

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

9. 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.

10. 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.

11. 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.

12. 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

13. 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.

14. 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)

15. 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

16. Advantages of
DBMS
1. Control of data redundancy
2. Data Consistency
3. Sharing of data
4. Improved security
5. Enforcement of standards
6. Economy of scale
7. Balance of conflicting requirements
8. Improved data accessibility and responsiveness.
9. Increased productivity
10. Increased maintenance through data independence.
11. Increased concurrency.
12. Improved backup and recovery services.

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