Distributed Information Systems (CSCI 5533) Presentation ID: 19

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Distributed Information Systems (CSCI
5533)Presentation ID 19

• Query Processing In Distributed Multi - DBMS
• Submitted to Dr. Liaw, Morris
• Submitted by Kumar, Manoj

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Distributed Multi-DBMS
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Overview of Multi-DBMS

• Its a layer of software
• Individual Query Processor

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Reasons for Query Processing Being complex in
Multi-DBMS than in Distributed DBMS

• 1. Difference in Capability of Component DBMSs
• 2. Complexity of Cost function
• 3. Difficulty in Moving Data between DBMSs
• 4. Local Optimization capability of each DBMS may
  be different

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Autonomy Issues

• 1. Communication Autonomy
• 2. Design Autonomy
• 3. Execution Autonomy

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• Architecture Of Distributed Multi-DBMS
• poses certain challenges too.
• Data is not only distributed across multiple
  sites but also across multiple databases which
  are individually managed.

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• Only 2 parties involve in case of Distributed
  DBMS
• Control site
• Local sites
• In Distributed Multi-DBMS 3 parties participate
• Multi-DBMS layer at control site
• Multi-DBMS layer at sites that process query
• Component DBMS

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Query Processing Layers in Distributed Multi-DBMS

• After Query is received at a site .
• Step 1 Split the query into subqueries based on
  data distribution across multiple sites
• - Global Directory (Data Allocation Info.)
• - this site is CONTROL SITE

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• Step 2 Subquery is sent to the site where it
  needs to be processed
• Step 3 Multi-DBMS layer at each site further
  fragments the query
• Step 4 Each subquery is Translated to
  respective DBMS language

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• In order to facilitate translation, Auxiliary
  database is used.
• Auxiliary database maintains extensive
  information about global query language and
  individual query languages used by DBMSs
• Step 5 Query submitted to Component DBMSs are
  processed

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• Decomposition
• Optimization
• Execution

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• Questions ??