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A View over Distributed databases
Vinod Bobba Illinois State university Billy Lim ITK 478 1/16/2019
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Agenda Introduction Point of view Conclusion
Distributed over Centralized Fragmentation Distributed Concurrency Control Conclusion 1/16/2019
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Distributed databases
Defining a global database as though it were centralized Distributing portions of it at a variety of interconnected sites Types Homogeneous Heterogeneous Gateway protocols 1/16/2019
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Distributed over centralized
Reflects organizational structure No single point failure Performance Modifications are easy 1/16/2019
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Data Replication Disadvantages
Reliability and Fast response May avoid complicated distributed transaction integrity routines De-couples nodes Disadvantages Additional requirements for storage space. Additional time for update operations. Integrity exposure of getting incorrect data if replicated data is not updated simultaneously. Therefore, better when used for non-volatile data. 1/16/2019
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Fragmentation Importance Horizontal Fragmentation
Breaking relations Horizontal Fragmentation Vertical Fragmentation 1/16/2019
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Fragmentation Allocating Fragments Minimize cost of transmission
Redundant Nonredundant Minimize cost of transmission Query type Linier Integer Formulation 1/16/2019
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Distributed Concurrency Control
Transactions Transaction manager Lock Management Centralized Primary Copy Fully Distributed Deadlock detection- wait for Phantom Deadlocks 1/16/2019
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Distributed Concurrency Control
Distributed Recovery Abort Transactions Commit protocols Two phase commit Coordinates activities at different sites involved in the transaction 1/16/2019
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Better Performance Exploit Parallelism Commercial Systems
Interquery Intraquery Commercial Systems Concurrency Control and recovery protocols are required – Synchronization 1/16/2019
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Problems Need Network Scaling Complex data New database technologies
Advanced replica control protocols Advanced transaction model Processing methods 1/16/2019
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Pros Increased Reliability and availability Local control over data
Modular growth Low communication cost Faster response for certain queries 1/16/2019
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Cons Processing overhead Data integrity exposure
Slower response for certain queries Software cost and complexity 1/16/2019
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Q&A Invite Questions 1/16/2019
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