Data communication, Components of data communication system, Distributed database, Features of distributed database , Advantages of Distributed Databases, Adversities of Distributed Databases,

1. Prof. Neeraj Bhargava
Pooja Dixit
Department of Computer Science
School of Engineering & System Science
MDS, University Ajmer, Rajasthan, India
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2.  Data communication
 Components of data communication system
 Distributed database
 Features of distributed database
 Advantages of Distributed Databases
 Adversities of Distributed Databases
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3.  Data communication refers to the exchange of data
between a source and a receiver via form of
transmission media such as a wire cable.
 The meanings of source and receiver are very simple.
 The meanings of source and receiver are very simple.
The device that transmits the data is known as source
and the device that receives the transmitted data is
known as receiver.
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4.  Message : It is the information or data to be
communicated. It can consist of text, numbers,
pictures, sound or video or any combination of
these.
 Sender: It is the device/computer that generates
and sends that message.
 Receiver: It is the device or computer that
receives the message.
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5.  Medium: It is the channel or physical path through
which the message is carried from sender to the
receiver. The medium can be wired like twisted pair
wire, coaxial cable, fiber-optic cable or wireless like
laser, radio waves, and microwaves.
 Protocol: It is a set of rules that govern the
communication between the devices. Both sender and
receiver follow same protocols to communicate with
each other.
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7.  A distributed database is a collection of multiple
interconnected databases, which are spread
physically across various locations that
communicate via a computer network.
 Computer workstations or remote devices (sites or
nodes) that form the network system.
 The distributed database system must be
independent of the computer system hardware.
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8.  Databases in the collection are logically interrelated with each
other. Often they represent a single logical database.
 A distributed database is not a loosely connected file system.
 The processors in the sites are connected via a network. They
do not have any multiprocessor configuration.
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9.  Modular Development − If the system needs to be
expanded to new locations or new units, in
centralized database systems,.
 More Reliable − In case of database failures, the total
system of centralized databases comes to a halt.
 Better Response − If data is distributed in an efficient
manner, then user requests can be met from local
data itself, thus providing faster response.
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10.  Need for complex and expensive software −
DDBMS demands complex and often expensive
software to provide data transparency and co-
ordination across the several sites.
 Processing overhead − Even simple operations
may require a large number of communications
and additional calculations to provide uniformity
in data across the sites.
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11.  Data integrity − The need for updating
data in multiple sites pose problems of
data integrity.
 Overheads for improper data
distribution − Responsiveness of queries
is largely dependent upon proper data
distribution. Improper data distribution
often leads to very slow response to user
requests.
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