Systems Design System Architecture

1. Systems Analysisand Design Systems Design System Architecture

2. 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

3. 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 • Security issues

4. System Architecture Checklist • Enterprise Resource Planning (ERP) • The objective of ERP is to establish a company-wide strategy for using IT resources. • Describes a specific hardware environment, also called a platform • Supply chain management (SCM) concept extends internal ERP to suppliers and customers

5. System Architecture Checklist • Initial Cost and TCO • During the final design stage, you make decisions that will have a major impact on the initial costs and TCO for the new system • You should review all previous cost estimates

6. 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? • Have any new types of outsourcing become available? • Have any significant technical developments occurred? • Answers might affect the initial cost and TCO for the proposed system

7. 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 • Important for dynamic, growing business

8. System Architecture Checklist • Web Integration • Web-centric architecture • Avoids many of the connectivity and compatibility problems that typically arise • E-marketplaces is the term describing Internet-based solutions for buyers and sellers.

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

10. 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

11. System Architecture Checklist • Security Issues • Security threats and defenses are a major concern to a systems analyst • The analyst must consider security issues that relate to system design specifications and determine how the company will address them • Web-based systems introduce additional security concerns

12. Planning the Architecture • Every information system involves three main functions: data storage and access methods, application programs to handle the processing logic, and an interface that allows users to interact with the system • Depending on the architecture, the three functions are performed on a server, on a client, or are divided between the server and the client

13. Planning the Architecture • Servers • Server • Clients • Mainframe architecture where the server performs all processing • A systems analyst should know the history of mainframe architecture to understand the server’s role in the modern system design

14. Planning the Architecture • Servers • Mainframe History • In addition to centralized data processing, early systems performed all data input and output at a central location, often called a data processing center • Users had no input or output capability, except for printed reports that were distributed by a corporate IT department

15. Planning the Architecture • Servers • Server-based processing • Terminal (keyboard and display units) • In a centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back • As server technology evolved, terminal technology also changed dramatically

17. Planning the Architecture • Clients • As PC technology exploded in the mid-1980s and 1990s, powerful microcomputers quickly appeared on corporate desktops • Users found that they could run their own word processing, spreadsheet, and database applications • Companies linked the stand-alone computers into networks

18. 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

19. Planning the Architecture • Clients • Local and wide area networks • Companies resolved the problems of stand-alone computing by joining clients into a local area network (LAN) • A wide area network (WAN) spans long distances and can connect LANs that are continents apart.

22. Planning the Architecture • Clients • Local and wide area networks • The network is transparent because user sees data as if it were stored on his/her own computer • Compared to mainframe architecture, distributed systems increase concerns about data security and integrity

23. Planning the Architecture • Clients • Client-based processing • In a typical LAN, clients share data stored on a local server • In a file server design, also called a file sharing architecture, an individual LAN client has a copy of the application program installed locally, while the data is stored on a central file server • A file server design requires significant network resources

25. Client/Server Architecture • Today’s interconnected world requires an information architecture that spans the entire enterprise • Whether you are dealing with a departmental network or a multinational corporation, as a systems analyst you will work with a distributed computing strategy called client/server architecture

26. Client/Server Architecture • Overview • Client/server architecturerefers to systems that divide processing between one or more networked clients and a central server • The client submits a request for information form the server, which carries out the operation and responds to the client • Many early client/server systems did not produce expected savings

29. Client/Server Architecture • Overview • 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

30. Client/Server Architecture • Client/Server Design Styles • Client/server designs can take many forms, depending on the type of server and the relationship between the server and the clients • In each case, the processing is divided between the server and the clients

32. Client/Server Architecture • Fat and Thin Clients • Fat client - thick client locates all or most of application processing logic at the client • Thin client locates all or most of application processing logic at the server • Most IT experts agree that thin client designs provide better performance, because program code resides on the server, near the data • In contrast, a fat client handles more of the processing and must access and update the data more often

34. Client/Server Architecture • Client/Server Tiers • Two-tier design; UI on client, data on server, application on both or on each • Three-tier design; UI on client, data on server, application on middle layer (application server), because it provides the application logic, or business logic • Three-tier designs also are called n-tier designs • The middle layer is more efficient and cost-effective in large-scale systems

37. 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

38. 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

39. Client/Server Architecture • Client/Server Performance Issues • Client/server architecture does involve performance issues that relate to the separation of server-based data and networked clients • 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 and makes as few trips as possible

40. Client/Server Architecture • Client/Server Performance Issues • Distributed database management system (DDBMS) • 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

41. Internet-Based Architecture • The Internet has had an enormous impact on system architecture • The advantages of Internet-based architecture are changing fundamental ideas about how computer systems should be designed, and many IT experts are shifting their focus to a total online environment

42. Internet-Based Architecture • Developing E-Commerce Solutions In-House • If you decide to proceed with an in-house solution, you must have an overall plan to help achieve your goals • An in-house solution usually requires a greater initial investment, but provides more flexibility for a company that must adapt quickly in a dynamic e-commerce environment

44. Internet-Based Architecture • Packaged Solutions and E-commerce Service Providers • Many vendors offer turnkey systems for companies • Use an application service provider (ASP) that provides applications or access to applications • Use managed hosting; implement, update, troubleshhot, patch, monitor, administer, backup data • Consider the experience of other companies in the same industry, success stories

45. Internet-Based Architecture • Corporate Portals • A portal is an entrance to a multifunction Web site • A corporate portal can provide access for customers, employees, suppliers, and the public

46. Internet-Based Architecture • Cloud Computing; cloud often represents Internet • A user’s computer does not perform processing or computing tasks • Effectively eliminates compatibility issues • Scaling on demand; matches resources to needs • Requires significantly more bandwidth • Advances continue to make cloud computing more feasible, desirable, and secure

48. Internet-Based Architecture • Web 2.0 • Envisions a second generation of the web that will enable people to collaborate, interact, and share information more dynamically • Wiki; web-based repository that anyone can access, contribute and modify • Internet operating system are layers of information added (text, sound bytes, images, video clips) and shared

49. Processing Methods • Online Processing • An online system handles transactions when and where they occur and provides output directly to users • Because it is interactive, online processing avoids delays and allows a constant dialog between the user and the system • Online processing also can be used with file-oriented systems