12 Chapter 12 Client/Server Systems Database Systems: Design, Implementation, and Management, Fifth Edition, Rob and Coronel

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 2 In this chapter, you will learn: What client/server computing is What the advantages of using client/server systems are How client/server systems evolved About client/server systems components and how they interact What effect the client/server system has on the DBMS How client/server systems might be introduced into an organization What factors affect the implementation of client/server systems

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 3 Client/Server Computing Computing model for the development of computerized systems –Client requests specific service –Server provides requested service Reside on same or different computers Figure 12.1

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 4 Client/Server Computing (con’t.) Key to client server power is where request processing takes place Extent of sharing processing –Thin client –Thin server –Fat client –Fat server Classification –2-tier –3-tier

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 5 Forces that Drive Client/Server Trend Changing business environment Growing need for enterprise data access Demand for end-user productivity gains based on efficient use of data Technological advances Growing cost/performance advantages

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 6 Evolution of Computing Environment Figure 12.2

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 7 Mainframe vs. Client/Server Systems Table 12.1

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 8 Managerial Expectations of Client/Server Systems Client/Server efficiency functions –Platform independent development –Optimized distribution of processing activities among different platforms –User friendly and cost effective techniques, methodologies, and specialized tools Observations –Tool, not end goal –Not answer to all data management problems –Has own set of management problems

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 9 MIS Expectations of Client/Server Benefits Reduced development and implementation costs Reduced development time and increased programmer productivity Extended system life cycle through scalability and portability Reduced system operational cost Change of MIS function from development to end- user support Enhanced information deployment

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 10 Organizational Expectations of Client/Server Benefits Flexibility and adaptability Improved employee productivity Improved company work flow and way to reengineer business operations New opportunities for competitive advantages Increased customer service satisfaction

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 11 Client –Front-end application Server –Back-end application Communications middleware –Communications layer Components of Client/Server Architecture Figure 12.3

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 12 Example Client/Server Architecture Figure 12.4

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 13 Client/Server Principles Hardware independence Software independence –Operating systems –Network systems –Applications Open access to services Process distribution –Process autonomy –Maximization of local resources –Scalability and flexibility –Interoperability and integration Standards

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 14 File services Print services Fax services Communications services Database services Transaction services Miscellaneous services Server Components

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 15 Server Components Figure 12.6

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 16 Fast CPU Fault-tolerant capabilities –Dual power –Standby power –Error checking and correcting memory –RAID Expandability of CPU, memory, disk, and peripherals Bus support for multiple add-on boards Multiple communications options Typical Characteristics of Server Hardware

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 17 Location independence Resource optimization Scalability Interoperability and integration Server Process Benefits

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 18 Database Middleware Network independence –Front-end application accesses data without regard to network protocols Database server independence –Generic SQL to access different database servers –Isolates programmer from SQL dialect differences

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 19 Two levels –Physical level Client and server computers –Logical level Client and server processes Interprocess communication (ICP) protocols Communications Middleware

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 20 OSI Network Reference Model Table 12.2

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 21 Information Flow through OSI Model Figure 12.7

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 22 Transport Process ID Figure 12.8

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 23 Transmission Control Protocol/Internet Protocol (TCP/IP) Internetwork Packet Exchange/ Sequenced Packet Exchange (IPX/SPX) Network Basic Input Output System (NetBIOS) Application Program to Program Communications (APPC) Network Protocols

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 24 Database Middleware Components Figure 12.9

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 25 Interactions between Middleware Components Figure 12.10

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 26 Middleware Accessing Multiple Database Servers Figure 12.11

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 27 Middleware Accessing Mainframe Databases Figure 12.12

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 28 Messaging-oriented middleware (MOM) Remote-procedure-call-based (RPC-based) middle ware Object-based middleware Middleware Classifications

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 29 Client operating systems –Microsoft Windows –OS/2, Apple Mac OS, Unix, Linux Client graphical user interfaces –Microsoft Windows –OS/2 Presentation Manager, Macintosh, UNIX Server operating systems and network protocols –Database servers: Unix, OS/2, Windows NT Server/2000 Server –Printer and file servers: Novell Netware –LAN protocols: TCP/IP, IPX/SPX, NetBIOS Middleware –ODBC, IDAPI, DRDA, Q+E Competing Standards

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 30 Transparent data access to multiple, heterogeneous clients Allow client requests to the database server over network Process client data requests at local server Send only SQL results to clients over network Client/Server DBMS Functions

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 31 Application Logic Components Figure 12.14

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 32 Two Key Questions –How is the division made? –Where should the results of division be placed? Five Functional Logic Components –Presentation logic –I/O processing logic –Application of business logic –Data management logic –Data manipulation logic Client/Server Architectural Styles

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 33 Application Functional Components Figure 12.15

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 34 Functional Logic Splitting Figure 12.16

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 35 Proprietary to open systems Maintenance-oriented coding to analysis, design, and service Data collection to data deployment Centralized to distributed style Vertical, inflexible to horizontal, flexible organizational style Differences in IS components Client/Server versus Traditional DP

12 Database Systems: Design, Implementation, & Management, 5 th Edition, Rob & Coronel 36 Management Issues –Communications infrastructure –Applications –Controlling escalating and hidden costs –People and cultural changes –Multiple vendor relationships Development tool acquisition Determination if client/server approach is correct Client/Server Implementation Issues