DISTRIBUTED DATABASES

1) a) Why the top three layers in the reference architecture for distributed database systems are often referred to as site-independent schemas? Define physical image of a global relation at a site.

b) Comment on the different types of dependency for the bottom layers in the reference architecture of DDBMS. Explain the role of local mapping schema towards the integration of heterogeneous multi-site databases in this context.

2) a) Differentiate between transaction recovery and crash recovery. Briefly explain the objectives of distributed transaction management.

3) a) Write down the responsibilities of transaction manager and transaction coordinator.

b) Define distributed serializability. How is it ensured in a DDBMS?

4) a) Compare and contrast Pessimistic and Optimistic Concurrency Control techniques.

5) Describe quorum-based protocol for distributed concurrency control.

6) Discuss how distributed systems are used in organizations

7) Discuss the techniques used to facilitate distributed query processing and Optimization.