l7 - Distributed Databases

8/3/2019 l7 - Distributed Databases

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DISTRIBUTED PROCESSING

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DISTRIBUTED DATABASES


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DISTRIBUTED DATABASES

When the computer system and the databases arefound at one location, they are called centralizeddatabases,

when they are scattered they are called distributeddatabase systems


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DISTRIBUTED PROCESSING

Distributed processing can be defined as a system inwhich both computer power and data occur at more

than one site, and application programs are run at

more than one site

Earlier distributed processing systems were

considered uneconomical because of the economies

of scale associated with large centralized computer

systems


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DISTRIBUTED DATABASES When processing is distributed, then data too needs

to be distributed and made available at the differentlocations.

There are two ways of doing this

Replicated databases

- provide duplicates of all data at all sites

Partitioned databases

- data may be divided into segments and madeavailable to diff locations. Partition could be alongfunctional lines, sales, finance etc or geographical lines


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ADVANTAGES & DISADVANTAGES

Distributed databases reduce costs of transferringdata to diff sites

Provide faster response time for filling forms etc.

However problems of control are compounded Problems of security are increased

Data redundancy occurs and consistency iscompromised

When managers download data from a centralizeddatabase to their own computers, it is no longercentralized


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REASONS FOR IMPLEMENTATION

Improved response time Reduced costs

Improved accuracy

Reduced mainframe costs Smoother growth

Increased reliability

Resource sharing

Increased user satisfaction


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CONCERNS FOR MANAGERS

Lack of professional MIS staff Standardization

Documentation

Data loss Security

Data consistency

System maintenance


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AN EFFECTIVE SYSTEM

Distributed processing systems have to be managedcarefully in order to be effective.

The systems should: Be easy to use.

Users should not have to know where the data is, or which

processors need to be used


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CLIENT / SERVER COMPUTING

This is most commonly used now a days. Theapplication processing is divided between a client

which is generally a PC and a server, which may be

a file server on a local area network or a

minicomputer or a mainframe.

The client processes run on the PC and make

requests of the server processes, which may run on

several platforms


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SQL SERVERS An SQL server is a software package that runs on a

dedicated networked computer The SQL server computer usually devotes all its energies to

managing the database software and does not handle othernetwork tasks

SQL server software performs database applications fasterand more reliably than typical LAN based databasemanagement software

A client workstation may ask SQL server software to send allrecords that match certain selection parameters. The SQL

server software will process the request at the server andsend only those records that fit the parameters

In client server computing, the back end processor providesaccess to the database and a variety of database servicessuch as remote connectivity and data security


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DOWNSIZING

Makes available the data in any of the organizationsdatabases to any one with a microcomputerworkstation

Because of their power and efficiency, client server

computing systems running on LANs have beenreplacing mainframe bases information systems inmost organizations

Most organizations are downsizing to LAN basedclient server computer systems from older legacysystems


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THANK YOU

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Practice Questions Q1. Explain the term distributed processing? How does distributed

processing differ from a distributed database.

Q2. Is it necessary for organization to implement distributed processing?Support your answer by Giving Reason

Q3. What are the two basic ways to distribute database? Explain how thismethod differs?

Q4. Why might an organization want to have a distributed database system?

Q5. What problem distributed database system might generate for anorganization?

Q6. Explain how client / server information systems can help managers

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l7 - Distributed Databases

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