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Distributed Information Systems (CSCI 5533) Presentation ID: 19

Distributed Information Systems (CSCI 5533) Presentation ID: 19. Query Processing In Distributed Multi - DBMS Submitted to: Dr. Liaw, Morris Submitted by: Kumar, Manoj. Distributed Multi-DBMS. Overview of Multi-DBMS. It’s a layer of software Individual Query Processor.

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Distributed Information Systems (CSCI 5533) Presentation ID: 19

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  1. Distributed Information Systems (CSCI 5533)Presentation ID: 19 Query Processing In Distributed Multi - DBMS Submitted to: Dr. Liaw, Morris Submitted by: Kumar, Manoj

  2. Distributed Multi-DBMS

  3. Overview of Multi-DBMS • It’s a layer of software • Individual Query Processor

  4. 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

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

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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

  11. Decomposition • Optimization • Execution

  12. Questions ??

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