JNTU
JNTU MCA 2018 DISTRIBUTED DATABASES Previous Question Paper (June/July - 2018 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
Part A
5 x 5 Marks = 25
What are the advantages of a distributed database management system over a centralized DBMS?
Answer
A distributed database management system (DDBMS) offers several advantages over a centralized system: 1) Local Autonomy: Sites can manage their own data locally while still participating in the global system. 2) Improved Reliability and Availability: If one site fails, the entire system does not necessarily crash, and data can be replicated across multiple nodes. 3) Performance: Data is stored closer to the site where it is most frequently accessed, reducing communication overhead and latency. 4) Modularity and Scalability: The system can be expanded by adding new sites without requiring major changes to the existing infrastructure.
Give the comparison of global queries and fragmented queries.
Answer
A Global Query is defined on the global conceptual schema, which represents the entire database as if it were centralized, hiding the distribution details from the user. In contrast, a Fragmented Query is defined on the physical fragments of the database. The query processor must perform query decomposition and localization to transform a global query into a fragmented query that can be executed against specific sites where the data fragments reside.
Discuss the ways in which the concurrency control approaches can be classified.
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Define reliability. What are the types of failures in distributed DBMS?
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Differentiate between DDBMS and MDBMS.
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Part B
5 x 10 Marks = 50
Why is data replication useful in Distributed Database and what typical units of data are replicated?
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Distributed databases can be fragmented in many ways. Define the term fragmentation and explain using real world examples any three types of fragmentation that can be carried out.
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What is query optimization? Give the framework for query optimization in distributed environment.
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List steps of query decomposition and explain any one from that.
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Consider a failure that occurs during 2PC for a transaction. For each possible failure, explain how 2PC ensures transaction atomicity despite the failure?
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Explain briefly about timestamp-based concurrency algorithms.
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Define a catalog. How is it maintained in distributed databases?
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Describe the role of check points and cold restart mechanisms in dealing with inconsistencies in transactions.
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Explain briefly about architectural issues in distributed object DBMS.
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Give objective of query processing in view of distributed database.
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