Chapter 9

Chapter Objectives Provide a checklist of issues to consider when selecting a system architecture Describe servers, server-based processing, clients, and client-based processing Explain client/server architecture, including tiers, cost-benefit issues, and performance Compare in-house e-commerce development to packaged solutions 3

Chapter Objectives Explain the difference between online and batch processing Define network topology, and provide examples of hierarchical, star, bus, and ring network models Describe wireless network standards, advantages, and disadvantages 3

Chapter Objectives Explain network protocols and licensing issues Explain performance measurement, fault management, backup, and disaster recovery Describe the systems design specification

Introduction An effective system combines elements into an architecture, or design, that is flexible, cost-effective, technically sound, and able to support the information needs of the business System architecture translates the logical design of an information system into a physical structure that includes hardware, software, network support, and processing methods 4

System Architecture Checklist The analyst must consider seven specific issues that will affect the architecture choice Enterprise resource planning (ERP) Initial and total cost of ownership (TCO) Scalability Web integration Legacy system interface requirements Processing options System security

System Architecture Checklist Enterprise Resource Planning (ERP) The objective of ERP is to establish a company-wide strategy for using IT resources Advantage: it describes a specific hardware and software environment ( platform) that ensure connectivity and easy integration of future system including in house software and commercial packages Supply chain management

System Architecture Checklist Initial Cost and TCO Ask questions like the following If in-house development was selected as the best alternative initially, is it still the best choice? If a specific package was chosen initially, is it still the best choice? Answers might affect the initial cost and TCO for the proposed system

System Architecture Checklist Scalability Scalability, also called extensibility, refers to a system’s ability to expand, change or downsize easily to meet the changing need of a business enterprise Especially important in implementing systems that are volume-rated, such as transaction processing systems

System Architecture Checklist Web Integration An information system includes applications Web-centric architecture that follows internet design protocols and enables a company to integrate the new application into its e-commerce strategy. Avoids many of the connectivity and compatibility problems that typically arise IBM uses E-marketplaces to describe internet based solutions that allow seller and buyers to automate procurement process and achieve substantial benefits

System Architecture Checklist Legacy System Interface Requirements The new system might have to interface with one or more legacy systems Interfacing a new system with legacy systems involves analysis of data formats and compatibility The analyst must know if the new application eventually will replace the legacy system

System Architecture Checklist Processing Options In planning the architecture, designers also must consider how the system will process data - online or in batches Provision must be made for backup and speedy recovery in the event of system failure

System Architecture Checklist Security Issues Security is a concern at every stage of system development Web-based systems introduce additional security concerns

Planning the Architecture Every information system involves three main functions: Data storage and access methods Application programs to handle the processing logic An interface that allow users to interact with system. Depending on the architecture the three function are performed on a server, on a client, or are divided between the server and the client.

Planning the Architecture Servers Server is a computer that supplies data, processing services, or other support to one or more computers called client The term mainframe architecture typically describes a multiuser environment where the server is significantly more powerful than the clients

Planning the Architecture Server-based processing In a centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back Today mainframe architecture used in credit card company or in bank.

Planning the Architecture Clients Stand-Alone Computing Stand-alone computing was inefficient and expensive Maintaining data on individual workstations raised major concerns about data security, integrity, and consistency It was impossible to protect and back up valuable business data, and companies were exposed to enormous risks This led to data inconsistency and unreliability

Planning the Architecture Local and wide area networks Most of the companies resolved the problems of stand alone computing by joining clients into local area network that allows sharing of data and hardware recourses. A wide area network (WAN) spans long distances and can connect LANs that are continents apart The network is transparent Compared to mainframe architecture, distributed systems increase concerns about data security and integrity

Planning the Architecture Clients Client-based processing

Client/Server Architecture Overview Client/server architecture refers to system that divide processing between one or more networked clients and a central server. In typical client/server system, the client handles the entire user interface, including data entry, data query, and screen presentation logic. The server stores the data and provides data access and database management functions.

Client/Server Architecture Overview The early client/server system was expensive. Few clear standards exist client needed powerful hardware and software to handle shared processing tasks. Many companies had an installed base of mainframe data, called legacy data, which was difficult to access and transport to a client/server environment The client/server concept continues to expand to include clients and servers outside the organization

Client/Server Architecture Client/Server Design Styles Depends on the style the processing is divided between the server and the clients The nature of communication is depends on the type of the server A database server process individual SQL commands. The transaction server handles a set of SQL commands. An object server exchanges object messages with clients. A web server sends and receives Internet based communication.

Client/Server Architecture A web server sends and receives Internet based communication.

Client/Server Architecture Types of Clients: Fat and Thin A fat client also called a thick client design locates all or most of the application processing logic at client. A thin client design locates all or most of the processing logic at the server. The table in next slide describes the characteristics of the fat and thin clients.

Client/Server Architecture Types of Clients: Fat and Thin

Client/Server Architecture Client/Server Tiers Two-tier designs The user interface resides on the client, all data resides on the server, and the application logic can run either on the server or on the client or be divided between the client and server. Three-tier design – n-tier designs The user interface runs on the client and the data stored on the server, a middle layer process the client requests and translates them into data access commands that can be understood and carried out by the server

Client/Server Architecture Client/Server Tiers Three-tier design – n-tier designs Think of the middle layer as an application server, because it provides the application logic, or business logic The middle layer is more efficient and cost-effective in large-scale systems

Client/Server Architecture Middleware Enables the tiers to communicate and pass data back and forth Provides a transparent interface that enables system designers to integrate dissimilar software and hardware Can integrate legacy systems and Web-based applications

Client/Server Architecture Cost-Benefit Issues Client/server systems enable the firm to scale the system in a rapidly changing environment Client/server computing also allows companies to transfer applications from expensive mainframes to less expensive client platforms Client/server systems reduce network load and improve response times

Client/Server Architecture Client/Server Performance Issues In contrast to the centralized system, a client/server design separates applications and data Client/server systems must be designed so the client contacts the server only when necessary

Client/Server Architecture Client/Server Performance Issues Another issue is the data storage. Data can be stored in in more than one location using Distributed database management system (DDBMS) . DDBMS has the following advantages: Data stored closer to users can reduce network traffic The system is scalable, so new data sites can be added without reworking the system design The system is less likely to experience catastrophic failure

Client/Server Architecture Client/Server Performance Issues DDBMS has also the following disadvantages: It can be more difficult to maintain controls and standards when data is stored in various locations The architecture of DDBMS is more complex and difficult to manage.

Internet-Based Architecture Developing E-Commerce Solutions In-House

Internet-Based Architecture Packaged Solutions and E-commerce Service Providers Many vendors offer ready to use systems for companies Another alternative is to use an application service provider (ASP) Must consider whether the advantage of lower initial cost outweighs the disadvantage of reduced flexibility later on

Internet-Based Architecture Corporate Portals A corporate portal can provide access for customers, employees, suppliers, and the public Oracle and SAP offer powerful enterprise portal software

Processing Methods Online Processing Online systems handles transactions when and where they occur and provide output directly to users Example can be an airline reservation system and ATM system.

Processing Methods

Processing Methods Online Processing Online processing systems have four typical characteristics: The system processes transactions completely when and where they occur Users interact directly with the information system Users can access data randomly The information system must be available whenever necessary to support business functions

Processing Methods Batch Processing In a batch processing system, data is collected and processed in groups, or batches The IT operations group can run batch programs on a predetermined schedule without user involvement; and Batch programs require significantly fewer network resources than online systems

Processing Methods Combined Online and Batch Processing Online processing offers an inherent advantage because data is entered and validated as it occurs Online processing is more expensive Backup and recovery for online processing is more difficult In many situations, batch processing is cost-effective, less vulnerable to system disruption, and less intrusive

Processing Methods Combined Online and Batch Processing An example can be the Point of Sale (POS)

Network Models A network allows the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users. When planning a network design, you must consider network terms and concepts, including the OSI model, network model tools, network topology, network protocol, licensing issues, and wireless network.

Network Models The OSI Reference Model The Open System Interconnection (OSI) model which describes how data actually moves from an application on one computer to an application on another network, consists of seven layers Network layer: defines network addresses and determines how data is routed over the network Data link layer: defines specific methods of transmitting data over the physical layer, such as defining the start and end of a data block Physical layer: contains physical components that carry data, such as cabling and connecters

Network Models Each layer performs specific function, as follow:

Network Topology Ring network: Resembles a circle of computers that communicate with each other. Data flows in only one direction One disadvantage is if a device fails, the devices downstream from the failed device cannot communicate with network

Hierarchical network: Network Topology Hierarchical network: One or more powerful servers control the network An example is retail chain, with central computer that stores data about sales activity and inventory levels and local computer handle store level operations.

Network Topology Bus network: A single communication path connects the network server, departmental server, workstations, and peripheral device An advantage is that devices can be attached or detached from the network at any point without disturbing the rest of the network. Disadvantage is that the performance can decline as more devices added

Network Topology Star network: Has a central computer with network devices connected to it At the center of the star which is called hub, a central server manages the network Disadvantage is that the entire network is depend on the central computer.

Network Models Network Protocols and Licensing Issues The network must use a protocol A popular network protocol is Transmission Control Protocol/Internet Protocol (TCP/IP) A familiar example of a TCP/IP protocol is the file transfer protocol (FTP)

Network Models Wireless Networks A wireless local area network, or WLAN Uses 802.11 protocol that is developed by Institute of Electrical and Electronics Engineers (IEEE) This standard referred to Wi-Fi which stands for wireless fidelity Although they have many advantages, wireless networks pose special concerns with regard to system security

Wireless Networks Bluetooth is another wireless communication that is very popular for short distance wireless communication On addition to 802.11 protocols for LANs, IEEE is working on 802.16 standards which is communication protocol for MANs (metropolitan area networks) these specification that IEEE calls Wireless MAN™ - WiMAX are expected to enable wireless multimedia applications with a range of up to 30 miles

System Management and Support Performance Management Performance management tools are designed to collect information about system resources and activity levels Firms such as NetScout Systems offer comprehensive performance management packages The NetScout Web site mentions studies that show network delays cost the industry more revenue than actual stoppages

System Management and Support Fault Management, Backup, and Disaster Recovery Fault management Includes monitoring the system for signs of trouble, logging all system failures, diagnosing the problem, and applying corrective action

System Management and Support Fault Management, Backup, and Disaster Recovery Backup and disaster recovery Backup Recovery Disaster recovery plan Backup and recovery planning depends on the type of system involved

System Management and Support Fault Management, Backup, and Disaster Recovery Backup and disaster recovery Another common strategy is to use a RAID (redundant array of independent disks) system RAID systems are called fault-tolerant because the failure of any disk does not disable the system Experienced IT professionals often note that the three most important system security tools are backup, backup, and more backup

Systems Design Completion System Design Specification A typical system design specification uses a structure similar to the following: Executive summary (brief over view of the job) System components (design of input/output, data, and network) System environment (constrains, or conditions, affecting the system) Implementation requirements (start up process, initial data entry, training requirement and software test) Time and cost estimates Appendices provide supplemental material

Systems Design Completion User Approval Users must review and approve the interface design, report and menu designs, data entry screens, source documents, and other areas of the system that affect them When the system design specification is complete, you distribute the document to a target group of users, IT department personnel, and company management

Systems Design Completion Presentations The presentations give you an opportunity to explain the system, answer questions, consider comments, and secure final approval The first presentation is to the systems analysts, programmers, and technical support staff members Your next presentation is to department managers and users from departments affected by the system

Systems Design Completion Presentations The final presentation is for company management Key objective: to obtain management’s approval and support for the next development step Management might reach one of three decisions: proceed with systems development, perform additional work on the systems design phase, or terminate the project

Chapter Summary An information system combines hardware, software, data, procedures, and people into a system architecture The analyst must consider enterprise resource planning, initial cost and TCO, scalability, Web integration, legacy interface requirements, security, and processing options System security is an important concern An architecture requires servers and clients 49

Chapter Summary Compared to file server designs, client/server systems are more scalable and flexible In implementing a design, an analyst should consider e-commerce strategies, the availability of packaged solutions, and corporate portals, which are entrances to a multifunction Web site The primary processing methods are online and batch processing 49

Chapter Summary Networks allow the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users The way a network is configured is called the network topology The system design specification presents the complete systems design for an information system Chapter 9 complete 49