Associate Professor Dr. Raed Ibraheem Hamed
Department of IT and Computer Science _ UHD 1
University of Human Development, College of Science and Technology
Departments of IT and Computer Science
2015 – 2016
Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/2
Outline
• Background File Systems
• Database Management
• Motivation
• Distributed Computing
• What is a Distributed Database System?
• What is a DDBS
• Centralized DBMS on a Network
• Distributed DBMS Architecture
• Generic DBMS Architecture
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/3
Background File Systems
program 1
data description 1
program 2
data description 2
program 3
data description 3
File 1
File 2
File 3
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/4
Database Management
database
DBMS
Applicationprogram 1(with data
description)
Applicationprogram 2(with data
description)
Applicationprogram 3(with data
description)
description
manipulation
control
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Motivation
DatabaseTechnology
ComputerNetworks
distribution
DistributedDatabaseSystems
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Database Technology + Computer Networks =
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Distributed Computing
• A number of independent processing elements (not necessarilyhomogeneous) that are interconnected by a computer networkand that cooperate in performing their assigned tasks.
• What is being distributed?
➡ Processing
➡ Function
➡Data
➡Control
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/7
What is a Distributed Database System?
A distributed database (DDB) is a collection of multiple, logicallyinterrelated databases distributed over a computer network.
A distributed database management system (D–DBMS) is thesoftware that manages the DDB and provides an accessmechanism that makes this distribution explicit to the users.
Distributed database system (DDBS) = DDB + D–DBMS
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What is not a DDBS?
• A timesharing computer system
• A Widely or narrowly coupled multiprocessor system
• A database system which resides at one of the nodes of a network of computers - this is a centralized database on a network node
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/9
Centralized DBMS on a Network
Site 5
Site 1
Site 2
Site 3Site 4
CommunicationNetwork
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Distributed DBMS Environment
Site 5
Site 1
Site 2
Site 3Site 4
CommunicationNetwork
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/11
Distributed DBMS Promises
Explicit management of distributed, fragmented, and replicated data
Improved reliability/availability through distributed transactions
Improved performance
Easier and more economical system expansion
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Distributed DBMS © M. T. Özsu & P. Valduriez Ch.1/12
Distributed Database - User View
Distributed Database
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Distributed DBMS - Reality
CommunicationSubsystem
DBMSSoftware
UserApplicationUser
Query
DBMSSoftware
DBMSSoftware
DBMSSoftware
UserQuery
DBMSSoftware
UserQuery
UserApplication
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Architecture
•Defines the structure of the system
➡components identified
➡functions of each component defined
➡interrelationships and interactions between components defined
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Generic DBMS Architecture
ExternalSchema
ConceptualSchema
InternalSchema
Internal view
Users
External view
Conceptual view
External view
External view
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