Fall.pptVIP

Chapter 9 2013 Fall * Chapter 9: The Client/Server Database Environment 楊立偉教授 台灣大學工管系 註 : 於11版為Chapter 8 * Client/Server Systems Networked computing model 網路運算模型 Processes distributed between clients and servers 將要處理的工作散在Client與Server Client–Workstation (usually a PC) that requests and uses a service Server–Computer (PC/mini/mainframe) that provides a service For DBMS, server is a database server * Application Logic in C/S Systems GUI (Graphic User Interface) Procedures, functions, programs DBMS activities Processing Logic 處理邏輯 I/O processing Business rules Data management Storage Logic 儲存邏輯 Data storage/retrieval Presentation Logic 呈現邏輯 Input–keyboard/mouse Output–monitor/printer * 3 types of Client/Server Architectures 1.File Server Architecture 2.Database Server Architecture 3.Three-tier Architecture Client does extensive processing Client does little processing * 1. File Server Architecture All processing is done at the PC that requested the data Entire files are transferred from the server to the client for processing Ex. 利用網路芳鄰分享MDB檔 Problems: Huge amount of data transfer on the network Each client must contain full DBMS Heavy resource demand on clients Client DBMSs must recognize shared locks, integrity checks, etc. FAT CLIENT * Figure 9-2 File server model FAT CLIENT * 2. Two-Tier Database Server Architectures Client is responsible for I/O processing logic Some business rules logic Server performs all data storage and access processing ? DBMS is only on server * Advantages of Two-Tier Approach Clients do not have to be as powerful Greatly reduces data traffic on the network Improved data integrity since it is all processed centrally Stored procedures : performs some business rules done on server 把較常用或重要的程序預先寫好放在DBMS內 * Advantages of Stored Procedures Compiled SQL statements 編譯後執行快 Reduced network traffic 佔較少的網路流量 Improved security 安全性較高 Improved data integrity 資料完整性較高 Thinner clients 前端運算量較少 * Figure 9-3 Database server architecture (two-tier)