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GATE CS 2018 - Database Quiz- 3 (Transactions and Concurrency Control )
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Question 1
Consider a simple checkpointing protocol and the following set of operations in the log.
(start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (checkpoint);
(start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3), (write, T3, z, 7, 2);
If a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?
(start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7); (checkpoint);
(start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3), (write, T3, z, 7, 2);
If a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list?
Question 2
Consider the following schedule S of transactions T1, T2, T3, T4:
Which one of the following statements is CORRECT?
Which one of the following statements is CORRECT?
Question 3
Consider the following two-phase locking protocol. Suppose a transaction T accesses (for read or write operations), a certain set of objects {O1,....Ok}. This is done in the following manner:
Step 1. T acquires exclusive locks to O1,.....,Ok in increasing order of their addresses.
Step 2. The required operations are performed.
Step 3. All locks are released
This protocol will
Question 4
Two transactions T1and T2 are given as:
where
denotes a read operation by transaction 
on a variable V and 
denotes a write operations by transaction 
on a variable V. The total number of conflict serializable schedules that can be formed by 
and 
is ______.
where
denotes a read operation by transaction on a variable V and denotes a write operations by transaction on a variable V. The total number of conflict serializable schedules that can be formed by and is ______.Question 5
Consider 3 transactions T1 T2 and T3 having 2, 3 and 4 operations respectively. Find number of concurrent schedules.
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