Chapter Objectives

1. Chapter 9

2. 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

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

5. 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

6. 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

7. System Architecture Checklist Enterprise Resource Planning (ERP) The objective of ERP is to establish a company-wide strategy for using IT resources Describes environment – platform Specific hardware and software Supply chain management Extends ERP systems to suppliers and customers

8. 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? See list of questions on pages 401 – 402 Basically you need to review the four feasibilities: operational, technical, schedule, and economic Answers might affect the initial cost and TCO for the proposed system

9. 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

10. System Architecture Checklist Web Integration Will the new system be part of an e-commerce solution? Web-centric architecture or just a front-end to other systems? Avoids many of the connectivity and compatibility problems that typically arise when different hardware environments are involved E-marketplaces

11. 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 Converting data is time consuming and expensive The analyst must know if the new application eventually will replace the legacy system

12. System Architecture Checklist Processing Options In planning the architecture, designers also must consider how the system will process data: Online Batch Provision must be made for backup and speedy recovery in the event of system failure 24/7 systems – when do you backup? Batch easier to backup than online

13. System Architecture Checklist Security Issues Security is a concern at every stage of system development Web-based systems introduce additional security concerns System security in Chapter 11

14. Planning the Architecture Servers Server Clients The term mainframe architecture typically describes a multiuser environment where the server is significantly more powerful than the clients

15. Planning the Architecture Servers Server-based processing In a centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back

16. 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, data 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

17. Planning the Architecture Clients Local and wide area networks A wide area network (WAN) spans long distances and can connect LANs that are continents apart The network is transparent to the user Compared to mainframe architecture, distributed systems increase concerns about data security and integrity

18. Planning the Architecture LAN

19. Planning the Architecture WAN

20. Planning the Architecture Client-based processing – File Server example

21. Client/Server Architecture Overview Client/server architecture 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

22. Client/Server Architecture File Server compared to Client/Server Design

23. Client/Server Architecture

24. Client/Server Architecture Client/Server Design Styles

25. Client/Server Architecture Types of Clients: Fat and Thin

26. Client/Server Architecture Client/Server Tiers Two-tier designs 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

27. Client/Server Architecture

28. 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

29. 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 Using common languages such as SQL allows for communicating across different platforms Client/server systems reduce network load and improve response times

30. Client/Server Architecture Client/Server Performance Issues Client/server architecture involves performance issues that relate to the separation of server-based data and the networked clients that must access the data When the number of clients and the demand for services increases beyond a certain level, network capacity becomes a constraint, and system performance declines dramatically Developers must consider the number of users, network traffic, server size and location for current and future business needs Client/server systems must be designed so the client contacts the server only when necessary

31. Client/Server Architecture Client/Server Performance Issues Data storage location is a factor in Distributed Database Management Systems (DDBMS) DDBMS has advantages: data is stored closer to the user which reduces network traffic, the system is scalable and new data sites can be added, and less likely to experience a catastrophic failure DDBMS disadvantages: data security – more difficult to maintain controls and standards, it’s more complex and more difficult to maintain Most companies want it both ways: the control of a centralized system and the flexibility of a distributed system

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

33. Internet-Based Architecture In-house strategy benefits: Unique look and feel that matches overall company marketing materials Complete control over design Scalable More flexible when modifications are needed Can integrate with other company systems

34. Internet-Based Architecture Packaged Solutions and E-commerce Service Providers Many vendors offer turnkey 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

35. Internet-Based Architecture Corporate Portals A corporate portal can provide access for customers, employees, suppliers, and the public Main benefit empowers users and enables self-service access to enterprise content and services

36. 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 Examples: ATM and POS

37. 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 Examples: printing bills, paychecks, and updating customer accounts with credit card transactions, and updating accounting files from daily sales transactions

38. 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

39. Processing Methods Combined Online and Batch Processing

40. Network Models The OSI Reference Model The OSI model consists of seven layers Shows how data proceeds down through the seven layers on the transmitting computer, and then up through the seven layers on the receiving computer Important: OSI is a logical model and is not tied to any specific physical environment or hardware

41. Network Models The OSI Reference Model The OSI model consists of seven layers Application layer: provides network services requested by local workstation Presentation layer: assures that data is uniformly structured and formatted for network transmission Session layer: defines control structures that manage the communications link between computers Transport layer: provides reliable data flow and error recovery

42. Network Models The OSI Reference Model The OSI model 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

43. Network Models Network Topology Hierarchical network Star network Bus network Ring network

44. Network Models Network Topology - Hierarchical network

45. Network Models Network Topology – Star network

46. Network Models Network Topology – Bus network

47. Network Models Network Topology - Ring network

48. 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) Ethernet Token Ring

49. Network Models Wireless Networks A wireless local area network, or WLAN 802.11 Institute of Electrical and Electronics Engineers (IEEE) Wi-Fi – wireless fidelity Although they have many advantages, wireless networks pose special concerns with regard to system security Security will be discussed in Chapter 11

50. Network Models Wireless Networks BlueTooth On addition to 802.11 protocols for LANs, IEEE is working on 802.16 standards MANs (metropolitan area networks) WirelessMAN™ - WiMAX

51. 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

52. System Management and Support Fault Management, Backup, and Disaster Recovery Every system can experience problems: hardware failures, software errors, user mistakes, and power outages. Also, hackers and cyber-vandalism can cause a system to fail Fault management Includes monitoring the system for signs of trouble, logging all system failures, diagnosing the problem, and applying corrective action

53. System Management and Support Fault Management, Backup, and Disaster Recovery Best strategy is prevention: data validation, audit trail files, security measures, and other data controls Backup and disaster recovery Backup Recovery Disaster recovery plan Backup and recovery planning depends on the type of system involved

54. 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 Experienced IT professionals often note that the three most important system security tools are backup, backup, and more backup

55. System Management and Support Fault Management, Backup, and Disaster Recovery Backup and disaster recovery Log file or journal file Business insurance can help offset expenditures File retention laws and regulations apply to company data If a government rule specifies that a record of all payments to the company must be kept for three years, then your design must retain the data for that period

56. Systems Design Completion System Design Specification A typical system design specification uses a structure similar to the following: Executive summary – one to two pages System components – designs for input, output, UI, files, database, reports, etc. System environment – platform, data storage, and operational constraints Implementation requirements – startup plan, user training, and data conversion Time and cost estimates – detail for next phase and estimates for remaining SDLC phases Appendices

57. 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 Approvals obtained through out the design phase When the system design specification is complete, you distribute the document to a target group of users, IT department personnel, and company management

58. 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

59. 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 terminate the project

60. 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

61. 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

62. 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