Exercise Database Management Systems (CO3021) - Chapter 6: Concurrency Control Techniques

Question 6.1. State the purposes of concurrency control. Give several examples.
Question 6.2. What is a lock? Give an example.
Question 6.3. What is two-phase locking? How does it ensure serializability? Give an example.
Question 6.4. Differentiate the variations of the two-phase locking technique: conservative, strict,
rigorous.
Question 6.5. Describe deadlock and starvation problems and the approaches to dealing with them.
Give an example.
Question 6.6. What is a wait-for graph? How can it detect deadlock? 
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  1. Question 6.14. Describe the multiversion technique based on timestamp ordering. Give an example. Question 6.15. What is the main difference between the multiversion techniques and their corresponding basic techniques? Give an example. Question 6.16. Describe index locking. Give an example. Question 6.17. What are latches? When are they used? Question 6.18. What is an interactive transaction? Give an example. Question 6.19. What is a phantom record? Describe its problem for concurrency control. Question 6.20. Describe two-phase locking for insertions and deletions. Question 6.21. Given two following transactions. Form their schedule with read_lock, write_lock, and unlock operations using two-phase locking. Will deadlock occur with their execution? Explain in detail. Question 6.22. Consider the set of transactions accessing database element A. These transactions are operating under a basic timestamp-based scheduler. Explain why the transaction T3 has to be aborted. What happens if these transactions are operating under a multiversion timestamp-based scheduler? 2