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Database Distributed
Lulwah AL-Hazzani-200801363
Hadeel AL-Eissa-200801009
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Outline
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What is Distributed Database .
Architecture Database.
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The different types of DDB Design.
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Forms Of Distributed Data.
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Advantages Of Distributed Data.
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Disadvantages Of Distributed Data.
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What is Database Distributed
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A distributed database is a database in which storage
devices are not all attached to a common CPU.
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It may be stored in multiple computers located in the same
physical location, or may be dispersed over a network of
interconnected computers.
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Architecture Database
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A database user accesses the distributed database through:
Local applications
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applications which do not require data from other sites.
Global applications
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applications which do require data from other sites.
A distributed database does not share main memory or disks.
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Types Of DDB Design
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Non-Partitioned, Non- Replicated
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Partitioned, Non-Replicated
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Non-Partitioned, Replicated
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Partitioned, Replicated
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Forms Of Distributed Data
 There
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are five categories of distributed data:
replicated data.
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horizontally fragmented data.
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vertically fragmented data.
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reorganized data.
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separate-schema data.
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Replicated data.
 Replicated
data means that copies of the same data
are maintained in more than one location.
 Data
may be replicated across multiple machines
to avoid transmitting data between systems.
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Horizontally fragmented data.
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Horizontally fragmented data means that data is distributed
across different sites based on one or more primary keys.
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This type of data distribution is typical where,
for example, branch offices in an organization deal mostly with a
set of local customers and the related customer data need not to
be accessed by other branch offices.
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Vertically fragmented data.
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Vertically fragmented data is data that has been split by
columns across multiple systems.
The primary key is replicated at each site.
For example, a district office may maintain client
information such as name and address keyed on client
number while head office maintains client account balance
and credit information, also keyed on the same client
number.
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Reorganized data.
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Reorganized data is data that has been derived, summarized,
or otherwise manipulated in some way.
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This type of data organization is common where decisionsupport processing is performed.
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There may be some instances where the on-line transaction
processing (OLTP) and decision-support database
management systems are different.
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Decision-support typically requires better query
optimization and ad hoc SQL support than does OLTP.
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OLTP usually requires optimization for high-volume
transaction processing.
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Separate-Schema Data
 Separate-schema
data maintains separate
databases and application programs for different
systems.
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For example, one system may manage inventory and one
may handle customer orders.
There may be a certain amount of duplication with
separate-schema data.
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Advantages Of Distributed Data
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Increase reliability and availability.
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Easier expansion.
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Reflects organizational structure — database fragments are
located in the departments they relate to.
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Local autonomy or site autonomy — a department can control
the data about them (as they are the ones familiar with it.)
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Protection of valuable data — if there were ever a catastrophic
event such as a fire, all of the data would not be in one place, but
distributed in multiple locations.
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Improved performance — data is located near the site of
greatest demand, and the database systems themselves are
parallelized, allowing load on the databases to be balanced
among servers
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Disadvantages Of Distributed Data
Inexperience
— distributed databases are difficult to work with, and as
a young field there is not much readily available experience on proper
practice.
Lack
of standards — there are no tools or methodologies yet to help
users convert a centralized DBMS into a distributed DBMS.
Database
design more complex — besides of the normal difficulties, the
design of a distributed database has to consider fragmentation of data,
allocation of fragments to specific sites and data replication.
Additional
software is required.
Operating
System should support distributed environment.
Concurrency
timestamping.
control: it is a major issue. It can be solved by locking and
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References:
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Wikia, Database Management, DDBMS, Retrieved
11,May,2012 from
http://databasemanagement.wikia.com/wiki/Distributed_Da
tabase_Management_System_%28DDBMS%29
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Bunn.J.(2001), Distributed Database. Retrieved 11,May,2012
from
http://pcbunn.cacr.caltech.edu/DistributedDatabasesPakista
n.pdf
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Borysowich.C,(2007), Toolbox, Overview of Distributed
Database. Retreived 11,May,2012 from
http://it.toolbox.com/blogs/enterprise-solutions/overviewof-distributed-databases-16228
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Thank you for your listening