Chapter 3 : Distributed Data Processing

Business Data Communications, 6e

Centralized Data Processing

• Centralized computers, processing, data, control, support

• What are the advantages?– Economies of scale (equipment and personnel)– Lack of duplication– Ease in enforcing standards, security

Centralized Data Processing May Consist Of:

• Centralized Computers• Centralized Processing• Centralized Data• Centralized Control• Centralized Support Staff

Distributed Data Processing

• Computers are dispersed throughout organization

• Allows greater flexibility in meeting individual needs

• More redundancy• More autonomy

Why is DDP Increasing?

• Dramatically reduced hardware costs• Dramatically increased distributed

processing capabilities• Dramatically increased need for new

applications and shorter development times• Ability to share data across multiple

servers

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?

Benefits of DDP

• Responsiveness• Availability• Correspondence to

Org. Patterns• Resource Sharing• Incremental

Growth• Increased User

Involvement & Control

• Decentralized Operation & Control

• End-user Productivity

• Distance & Location Independence

• Privacy & Security• Vendor

Independence• Flexibility

Drawbacks of DDP

• More difficulty test & failure diagnosis• More dependence on communication technology• Incompatibility of components• Incompatibility of data

• More complex management & control• Difficulty in control of corporate information resources• Suboptimal procurement• Duplication of effort• Data integrity• Security

Client/Server Architecture

• Combines advantages of distributed and centralized computing

• Cost-effective, achieves economies of scale

• Flexible, scalable approach

Intranets

• Uses Internet-based standards & TCP/IP• Content is accessible only to internal users• A specialized form of client/server

architecture• Can be managed (unlike Internet)

Extranets

• Similar to intranet, but provides access to controlled number of outside users– Vendors/suppliers– Customers

Utilizing Web technologies

Distributed applications

• Vertical partitioning– One application dispersed among systems– Example: Retail chain POS, inventory,

analysis• Horizontal partitioning

– Different applications on different systems– One application replicated on systems– Example: Office automation

Other Forms of DDP

• Distributed devices– Example: ATM machines

• Network management– Centralized systems provide management and

control of distributed nodes

Distributed data

• Centralized database– Pro: No duplication of data– Con: Contention for access

• Replicated database– 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

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

Database Management Systems

• Structured collection of data for multiple applications to use

• Query language provides uniform access

Database Organization

1. Centralized – Common databases accessed by all processors

2. Replicated - Copy of central database stored at each processor

3. Partitioned – Individual databases for each processor

Centralized Databases

• Advantages

No duplication of data

Little reorganization required

• Disadvantages

Contention among multiple processors accessing a single database

Slow response time

Single point of failure

Replicated Databases

• Advantages

No processor-database contention

Shorter response time

During failure, new copy can be obtained

• Disadvantages

High storage cost

Redundant updates required

High reorganization costs

Partitioned Databases

• Advantages

No duplication of data

Size of database determined by application needs

Short response time

• Disadvantages

Ad hoc management reports must access multiple databases

Networking Implications

• What are the connectivity needs?

• What are the availability needs?

• What are the performance needs?