Database System Architectures Centralized vs ClientServer Architectures 1

Database System Architectures Centralized vs. Client-Server Architectures 1

Centralized m Mainframe / Centralized DBMS ® Processing ® User application programs ® User interface programs ® DBMS functionality m Dumb Terminals ® Display capabilities only ° 2

Client-Server m Decline of Hardware Prices m Dumb Terminals replaced with Personal Computers m Gradual Use of Processing Power on Client-Side m Two-Tier Architectures ® Servers with specialized functionality ® Clients provide user application programs and interface programs ° 3

Client-Server (two-tier) ° 4

Client-Server (two-tier) m Client side presented two problems preventing true scalability: ® ‘Fat’ client, requiring considerable resources on client’s computer to run effectively. ® Significant client side administration overhead. m By 1995, three layers proposed, each potentially running on a different platform. ° 5

Client-Server (three-tier) ° 6

Client-Server (three-tier) m Advantages: ® ‘Thin’ client, requiring less expensive hardware. ® Application maintenance centralized. ® Easier to modify or replace one tier without affecting others. ® Separating business logic from database functions makes it easier to implement load balancing. ® Maps quite naturally to Web environment. ° 7

Client Server Architecture ° 8

Thick client architecture ° 9

Thin ° client architecture 10

Application server architecture ° 11

Transactional application server architecture ° 12

The client-server architecture ° 13

(Totally) Distributed database systems ° 14