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Query Processing Challenges in Distributed Multi-DBMS Systems

This presentation delves into the complexities of query processing in Distributed Multi-DBMS systems compared to Distributed DBMS due to differences in component capabilities, cost functions, data movement challenges, and autonomy issues. The architecture of Multi-DBMS entails challenges in data distribution across various sites and databases, involving three parties for query processing. The query processing layers involve splitting queries, sending subqueries to relevant sites, fragmenting queries, translation to DBMS languages, and submission for processing. Learn about the intricacies and solutions in this realm.

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Query Processing Challenges in Distributed Multi-DBMS Systems

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Presentation Transcript

  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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