| Level: Master | Year: 2025 |
| Programme: ME/CS/MCIS | Full Marks: 50 |
| Course: Distributed Database System | Pass Marks: 30 |
| Time: 2hrs |
Candidates are required to give answers in their own words as far as practicable. The figures in the margin indicate full marks.
Question 1:
a. Explain the concept of distributed query optimization and its significance in improving the performance of distributed systems. Provide an example of a query and describe how a distributed query optimizer would optimize it. (5 Marks)
b. Consider a distributed database with the following fragmented relations:
CUSTOMERS_EU(CustomerID, Name, Country)
CUSTOMERS_US(CustomerID, Name, Country)
Write a distributed query to find all customers who are present in both regions. Describe the steps involved in executing this query in a distributed environment. (5 Marks)
Question 2:
a. Discuss the importance of transaction management in distributed database systems. Explain how distributed concurrency control mechanisms, such as locking and timestamp ordering, ensure data consistency across multiple sites. (5 Makrs)
b. Describe the INGRES and SDD – 1 algorithm and compare the performances of these algorithms. Provide an example scenario where OCC is used to handle conflicts between transactions. (5 marks)
Question 3:
a. Present an example of the execution of a distributed query in multiple sites when a database is fragmented as derived horizontal fragmentation. Include the figure illustrating the steps and query execution in different stages. (5 Marks)
b. Describe the role of the global recovery manager in a distributed database system. Explain how it coordinates with local recovery managers to handle site failures and ensure data reliability. Provide an example scenario where this coordination is crucial. (5 Marks)
Question 4
a. Discuss the role of LRM and illustrate the REDO and UNDO protocols. How atomicity and consistency are managed by commit protocols. (5 Marks)
b. Consider a scenario where a distributed database experiences a site failure. Describe the steps taken by the recovery manager to restore the site and ensure data integrity. Provide an example of a recovery process. (5 Marks)
Question 5
Write short notes on:
a. Simplification in Query Decomposition
b. Distributed Cost Model in Query Optimization