Chapter 3 : Distributed Data Processing

1. Chapter 3 : Distributed Data Processing Business Data Communications, 5e

2. Objectives • Difference between & Pros & Cons of Centralize & Distributed data processing (DDP) • Why DDP system needs data communications and networking • Different forms of DDP for applications • Different forms of DDP for distributed database. • Requirements of DDP for networking facilities • motivation towards Client/server.

3. Intro • Until recently only “data” type of information required to use communication. Now all 4 types of information (i.e. data, voice, video, image) use similar communication technology. • This chapter looks into different types of Data Communications • We look into two extreme Centralize & Distributed data processing. • The computing function in most organizations is implemented somewhere along a spectrumbetween these two extremes.

4. Centralized Data Processing • A Centralized Data Processing Centre may consists of: • Centralized computers, • Centralized processing, • Centralized data, • Centralized control, • Centralized support staff • The Basic advantages: • Economies of scale (equipment and personnel) • Lack of duplication • Ease in enforcing standards, security

5. Example of: Centralized Data Processing Dallas County Information Systems Architecture

6. Example of: Distributed Data Processing Facility is a WLAN that supports both data traffic and VoIP. The WLAN connects to the outside world via a satellite link that connects to the Internet, to Carnivals private wide area network (WAN), and to the public switched telephone network (PSTN) in the US. Carnival Valor Wireless LAN

7. Holiday Inn Information Systems

8. Distributed Data Processing • Computers are dispersed throughout organization with some means of interconnection among them • Allows greater flexibility in meeting individual needs • More redundancy • More autonomy

10. Why is DDP Increasing? Means and Motive: • Dramatically reduction in hardware costs • Dramatically increased distributed processing capabilities (Hardware capabilities) • Dramatically increased need for new applications and shorter development times • Ability to share data across multiple servers

11. DDP Pros & Cons • There are no “one-size-fits-all” solutions • Key issues • How does it affect end-users? • How does it affect management? • How does it affect productivity? • How does it affect bottom-line?

12. Responsiveness Availability Correspondence to Organizational Patterns Resource Sharing Incremental Growth Increased User Involvement & Control End-user Productivity Distance & location independence Privacy and security Vendor independence Flexibility Benefits of DDP

13. Drawbacks of DDP • More difficulty test & failure diagnosis • More components and dependence on communication means more points of failure • Incompatibility of components • Incompatibility of data • More complex management & control • Difficulty controlling information resources • Suboptimal procurement • Duplication of effort

14. Reasons for DDP • Need for new applications • On large centralized systems, development can take years • On small distributed systems, development can be component-based and very fast • Need for short response time • Centralized systems result in contention among users and processes • Distributed systems provide dedicated resources

15. Client/Server Architecture • Is Client/Server Distributed or Centralized? • Combines advantages of distributed and centralized computing • Positive aspects of Client/Server architecture: • Cost-effective, achieves economies of scale by centralizing support for specialized functions (e.g. file & database servers) • Provide universal access to information by authorized users • Flexible, scalable approach (File server & db server can be on the same computer, or db services can be provided by several geographically dispersed machines. Computers-Services can share processors for smaller Information systems or split among processors in larger systems to increase availability) • Example of Servers: Database, Printing & Fax, File Storage, Communication Front Ends, Gateways & Bridges

17. Intranets: Provides users the features and applications of the Internet but isolated within the organization. • Latest Development in DDP • Uses Internet-based standards, • e.g. Hyper Text Markup Language (HTML) and Simple Mail Transfer Protocol (SMTP) • Uses TCP/IP for LAN & WAN but isolated within an organization • Content is not accessible to public only accessible by the intended users • A specialized form of client/server architecture • Can be managed (unlike Internet)

18. Extranets • Based on Client/Server model for operation • Similar to intranet, but provides access to controlled number of outside users • Vendors/suppliers • Customers • Utilizing Web technologies, provides more than simple Web access rather extensive access to corporate resources in an enforced security environment.

19. Horizontal • Vertical Forms of Distributed Data Processing This general definition doesn’t show different forms of DDP • DDP System: Dispersed Interconnected Computing Facility in an organization • DDP can take one or more of the following forms: • Distributed Applications • Distributed Device Controllers • Distributed Control • Distributed Data

20. Distributed Applications • Two dimensions characterize the distribution of applications: • Allocation of Application Functions • Vertical or Horizontal

21. Distributed Applications (cntd.) • Allocation of Application Functions: • One application splits up into components that are dispersed among a number of machines • One application replicated on a number of machines • A number of different applications distributed among a number of machines

22. Distributed Applications (cntd.) 2. Partitioning Distributed Applications • Horizontal partitioning • Vertical partitioning

23. Distributed Applications (cntd.) • Horizontal Partitioned DDP • Different applications on different machines • One application replicated on a number of machines • In general Data Processing is distributed among a number of computers that have a peer relation, no Master/Slave relation, or no Client/Server concept. • Horizontal partitioning reflects: • Autonomous operation of computers • Load balancing • Organizational decentralization • Examples: • Office automation support system • Air traffic control system

24. Distributed Applications (cntd.) • Vertical Partitioned DDP • One application split up into components that are dispersed among a number of machines • Data processing is distributed in a hierarchical fashion. • Consists of a central computer system with one or more levels of satellite systems. • The nature of the partition reflects structure of the organization or the task or both. • The main Objective in Vertical Partitioned DDP: Assign processing load to the level of the hierarchy at which it is most cost-effective=>best features of both centralizes & DDP are combined • Examples: Insurance, Retail chain point-of-sale, Inventory, Process control

25. Distributed Devices • Controlling distributed set of devices that can via processors. For example: Automatic Teller Machines (ATM), laboratory interface, factory automation. • Factory automation contains distributed sensors, PLC, p.

26. Network Management • A Distributed System Requires: • Management and Control of Distributed System & Management of Communications facility including control of access to some of the facility. • Central Network Management System to interact with each computer in the system & each computer must include some management & control logic to be able to interact with the Central Network Management.

27. Distributed Database • Where portions of the data are dispersed among a number of computers. • Must include a DIRECTORY that identifies the location of each data element in the db. • 3 way of organizing: • Centralized • Replicated • Partitioned

28. Distributed data • Centralized database (often used with Vertical DDP, for security/integrity) • Pro: No duplication of data • Con: Contention for access • Replicated database (all or part copied in more than one computer, Real-Time, Near RT 30Minutes, Deferred-once or twice a day) • Pro: No contention • Con: High storage and data reorg/update costs • Partitioned database • Pro: No duplication, limited contention • Con: Ad hoc reports more difficult to assemble

29. Networking Implications • Connectivity requirements • What links between components are necessary? • Availability requirements • Percentage of time application or data is available to users • Performance requirements • Response time requirements