Wednesday, February 24, 2016

Fragmentation in Distributed Database - Quiz

Database System Architectures - Quiz

1. What are the advantages of Replication of data in Distributed database?
    Avaliability, Parallelism, Increased data transfer
    Availability, Parallelism, Reduced data transfer
    Availability, Increased parallelism, Cost of updates
    All of the above

2. A fragmentation technique wherein every tuple of a table is assigned to one or more fragments as a result of fragmentation is called ________________ .
    Vertical Fragmentation
    Horizontal Fragmentation
    Hybrid Fragmentation
    None of the above

Assume a relation EMP as given below:
                EMP(EmpNo, EName, Job, Sal, Department)
Furthermore, assume that there are two applications which are accessing the above mentioned table. One application typically retrieves information about employees who earn more than Rs5.000, the other application typically manages information about 'clerks' (job). Also, assume that there are employees with other designations and different salaries stored in EMP. With this information, answer the questions 3 to 6.

3. Which of the following are the simple predicates which can be directly extracted from the given applications?
    {Job = clerk, Salary>5000}
    {Job = clerk, Salary<5000}
    {Job = Manager, Salary>5000}
    {Job = Manager, Salary<5000}

4. How many valid minterm predicates we can derive for the above said problem?

5. Assume that the departments are 'Finance', 'Production', and 'Design'. If there is one more application which accesses the informatoin frequently based on the 'Finance' department, what would be the number of valid minterm fragments?

6. If by mistake, I miss one of the valid minterm fragments. What would be the effect of that in fragmentation?
    Causes skew
    Reconstruction of EMP will be unsuccessful
    Slows down the database access

7. Which of the following failures are unique to distributed database systems?
    Failure of a site
    Loss of messages
    Network Partition
    All the above

8. For the given set of simple predicates Pr, how many min-term predicates we can derive (including invalid ones). Pr = {Branch = “Vellore”, Branch = “Chennai”, Salary <=20000, Salary > 20000} Assumptions: Consider there are five different branches.

9. In a distributed database application, if we have very many number of read only queries than update queries then ______________ allocation technique is advantageous.
    Hybrid Fragmentation
    Horizontal Fragmentation
    Vertical Fragmentation

10. Which of the following would be the advantage of Database Fragmentation?
    Most of the operations are local to any sites
    Reduced Network Traffic
    Parallel processing
    All the above

Score =

Correct answers:

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