Transcript Chapter 3 : Distributed Data Processing

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:
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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
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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 processordatabase contention
• Disadvantages
High storage cost
Shorter response time
Redundant updates
required
During failure, new
copy can be obtained
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?