DBMS Architecture

Centralized DBMS Architecture

• Mainframe Computers: Used to process all system functions
  • Terminals provided only display capabilities, no processing
  • All processing performed on central system, display info sent to terminals
• Transition to Personal Computers
  • Terminals replaced by personal computers and workstations
  • Initially used similarly to display terminals, with centralized DBMS
  • Processing performed centrally, display info sent to user systems
• Evolution to Client-Server Architecture
  • Systems began utilizing user-side processing abilities

Client-Server Architecture

• Developed to manage a large number of personal computers, workstations, printers, file servers, etc., connected via a network
• Specialized Servers:
  • File servers: Maintain client machine files
  • Printer servers: Handle print requests from client machines
• Client Machines
  • Provide user interfaces to utilize server functionalities
  • Perform local processing
  • Connect to servers for additional functionalities
• Servers
  • Provide services like file access, printing, database access

Two-Tier Client-Server Architecture

• Evolution from Centralized Systems
  • User interfaces and application programs moved to client side
  • Query and transaction functionalities remain on server side
• Servers
  • Called Query Server/Transaction Server (SQL Server in RDBMS)
• DBMS Access
  • Application connects to DBMS via ODBC (Open Database Connectivity)
  • Client programs can connect to multiple RDBMS with ODBC API
  • JDBC (Java Database Connectivity) allows Java programs to access server-side DBMS
• Advantages
  • Simplicity
  • Compatibility with other systems

Three-Tier Client-Server Architecture

• Changes due to WWW
  • Led to new roles for clients and servers
• Intermediate Layer
  • Application server/Web server: Stores rules for accessing database
  • Accepts client requests, processes them, sends database commands
  • Acts as channel between database server and client
  • Further processes and filters data for user presentation (GUI format)
• Three Tiers
  • User Interface
  • Application Rules
  • Data Access

Summary

• Covered Centralized DBMS Architecture and Client-Server Architectures
• Two-Tier Architecture: Client and Server
• Three-Tier Architecture: Client, Application Server, Database Server

Hope these concepts are clear. Thank you.