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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