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Transcript of ditributed databases
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BrAinY 4Presented to:- Ma’am Asima Jamil & Class
GROUP MEMBERSZupashSanaMarhabaGROUP LEADER Hira Anwar
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DISTRIBUTED DATABASES
OUR TOPIC OF PRESENTATION IS
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Topics to be discussed are Centralized database system Distributed database Decentralized database Distributed DBMS Advantages and disadvantages of DDBMS Distributed database design Function of DDBMS Types of DDBMS DBMS transparency & gateways
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Centralized DB system Distributed DB system Decentralized DB system Distributed DBMS
Presented by
ZUPASH KIRAMAT
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Centralized Database systemA centralized database sometimes abbreviated CDB) is a database that is located, stored, and maintained in a single location. This location is most often a central computer or database system, for example a desktop or server CPU, or a mainframe computer
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Distributed DB system
database In a Distributed Database System the database is stored/spread physically across computers or sites in different locations that are connected together by some form of data communication network.
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Distributed DB system
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Difference
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Decentralized DB systemDatabase is stored on computers or sites on different location but the computers are not interconnected via a network.
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Distributed DBMS
A DDBMS is a centralized application that manages a distributed database as if it were all stored on the same computer.
Synchronizes all the data periodically, and in cases where multiple users must access the same data.
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ADVANTAGES AND DISADVANTAGES
SANA AYUB
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ADVANTAGES
Local control Reliability and availability Efficient querying process Modular growth Economics
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Advantages…
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Disadvantages
Software complexity and high costs
Processing overheads Data integrity Complex DB design Slow response
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DISTRIBUTED DB DESIGN
HIRA ANWAR
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Distributed DB designThree additional factors are involved
1.Data Fragmentation2.Data replication3.Data allocation
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Distributed Database Design
Fragmentation Relation may be divided into a number of
sub-relations, which are then distributed.
Allocation Each fragment has to be allocated to one or
more sites.
Replication Copy of fragment may be maintained at
several sites.
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Fragmentation
The DB may be broken into logical units.
Types Horizontal fragmentation• table broken into two or more set of
rows.
Vertical fragmentation• table broken into two or more set of
columns
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41
Horizontal and Vertical Fragmentation
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Data replication
A copy of each fragment may be stored at several sites.
Data replication is the design process of deciding which fragment will be replicated.
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Data Allocation
Each fragment have to be allocated to one or more sites, where it will be stored.
Three strategies used for this purpose:1. Fragmented data allocation.2. Complete replication3. Selective replication
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Fragmented data allocation. Database partitioned into disjoint fragments,
each fragment assigned to one site. Also called non-redundant allocation or
partitioned allocation.
Advantages:1. Efficiency2. SecurityDisadvantages3. Inconsistent access speeds4. Backup vulnerability
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Complete replication A complete copy of DB is maintained at
each site. No replication.
ADVANTAGES:1. Faster and consistent access speeds2. Reliability3. Node decouplingDISADVANTAGES:4. Update complexity5. Increased storage requirements
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Selective Replication Combination of partitioning, replication,
and centralization.
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Functions of DDBMS
EXTENDED COMMUNIICATION SERVICES: provides access to remote sites and allow transfer of queries.
EXTENDED SYSTEM CATALOG: (Global system catalog) to store data distribution details,
DUSTRIBUTED QUERY PROCESSING: Translate request at one site using local DBMS into proper request to another site using a different DBMS and data model.
EXTENDED CONCURRENCY CONTROL: to maintain concurrency of the replicated data.
EXTENDED RECOVERY SERVICES: to be able to recover from individual site crashes and failure of communication links.
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TYPES OF DDBMS
marhaba wazir
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What is it?
Cheerios
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What is it?
Trail Mix
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Types of Distributed Database System
Homogeneous Heterogeneous
DDBMS
Homogenous
Heterogeneous
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Homogenous Distributed Database Systems
In this type of database has all data center have same software
Much easier to design and manage.
It appears to user as a single system
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characteristics
Data are distributed Same DBMS is used Data managed by distributed DBMS Users access database through one
schema Global schema is the union of all
local DB schemas
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Homogeneous Database
Same software
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Heterogeneous Distributed Database Systems
In this type of database , Different data center may run different DBMS products, with possibly different underlying data models.
CHARACTERISICS• Data is distributed across nodes.• Different DBMS is used• Only local access databases can be accomplished using
only local DBMS and schema.• A global schema exists.
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Heterogeneous Distributed database
Sql oracle
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DBMS transparency & Gateways Transparency refers to ability to hide
the knowledge that local DBMSs may be different.
Applies to heterogeneous environment.
To achieve transparency, DBMSs at different sites should support the same interface.
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Gateways
Gateway provides following functions. Protocol for exchange of information between two
DBMSs. Mapping between two DBMSs data types. Mapping the SQL of the X system to that of Y. Mapping feedback information if the Y system to
that of the X. an effective mechanism to synchronize locking
and commit mechanism of Y system with those requested by X system.
Provide relational server function for the Y DBMS.
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http://www.slideshare.net/TAHAROC/types-of-data?from_action=save https://
www.google.com.pk/search?q=data+allocation+in+distributed+database+systems&espv=2&biw=1440&bih=799&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMI0Oj2vIWJyQIVxDSUCh2jVQ9q&dpr=1
https://www.google.com.pk/webhp?sourceid=chrome-instant&ion=1&espv=2&
ie=UTF-8#q=horizontal+and+vertical+fragmentation http://www.slideshare.net/Loveski/data-replication-in-distributed-
system?related=1