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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);
(checkpoint);
(start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3); (write, T3, z, 7, 2);
Q. 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
- a)Undo: T3, T1; Redo: T2
- b)Undo: T3, T1; Redo: T2, T4
- c)Undo: none; Redo: T2, T4, T3; T1
- d)Undo: T3, T1, T4; Redo: T2
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
Consider a simple checkpointing protocol and the following set of oper...
Since T1 and T3 are not committed yet, they must be undone. The transaction T2 must be redone because it is after the latest checkpoint.
Most Upvoted Answer
Consider a simple checkpointing protocol and the following set of oper...
The contents of the undo list and redo list in the given scenario are as follows:
Undo list: T3, T1
Redo list: T2
Explanation:
To understand the contents of the undo and redo lists, let's analyze the given set of operations and the checkpointing protocol.
1. The log begins with the operation (start, T4), which indicates the start of transaction T4.
2. The next operation is (write, T4, y, 2, 3), which signifies a write operation by transaction T4 on variable y with the old value 2 and the new value 3.
3. Then, we have (start, T1), which marks the start of transaction T1.
4. The operation (commit, T4) indicates that transaction T4 is being committed.
5. Next, we see (write, T1, z, 5, 7), which represents a write operation by transaction T1 on variable z with the old value 5 and the new value 7.
6. The checkpoint operation is denoted by (checkpoint), which is used to create a stable point for recovery.
7. After the checkpoint, we encounter (start, T2), indicating the start of transaction T2.
8. The operation (write, T2, x, 1, 9) signifies a write operation by transaction T2 on variable x with the old value 1 and the new value 9.
9. Next, we have (commit, T2), which denotes the commit of transaction T2.
10. The operation (start, T3) marks the start of transaction T3.
11. Finally, we see (write, T3, z, 7, 2), which represents a write operation by transaction T3 on variable z with the old value 7 and the new value 2.
Now, let's consider the crash scenario and the recovery process using undo and redo operations:
- When a crash occurs, the system needs to undo the incomplete transactions and redo the completed transactions after the last checkpoint.
- The undo list contains the transactions that need to be undone, i.e., the incomplete transactions after the last checkpoint. In this case, transactions T3 and T1 are the incomplete transactions after the checkpoint. Therefore, the undo list contains T3 and T1.
- The redo list contains the transactions that need to be redone, i.e., the completed transactions after the last checkpoint. In this case, transaction T2 is the only completed transaction after the checkpoint. Therefore, the redo list contains T2.
Hence, the correct answer is option A: Undo: T3, T1; Redo: T2.
Undo list: T3, T1
Redo list: T2
Explanation:
To understand the contents of the undo and redo lists, let's analyze the given set of operations and the checkpointing protocol.
1. The log begins with the operation (start, T4), which indicates the start of transaction T4.
2. The next operation is (write, T4, y, 2, 3), which signifies a write operation by transaction T4 on variable y with the old value 2 and the new value 3.
3. Then, we have (start, T1), which marks the start of transaction T1.
4. The operation (commit, T4) indicates that transaction T4 is being committed.
5. Next, we see (write, T1, z, 5, 7), which represents a write operation by transaction T1 on variable z with the old value 5 and the new value 7.
6. The checkpoint operation is denoted by (checkpoint), which is used to create a stable point for recovery.
7. After the checkpoint, we encounter (start, T2), indicating the start of transaction T2.
8. The operation (write, T2, x, 1, 9) signifies a write operation by transaction T2 on variable x with the old value 1 and the new value 9.
9. Next, we have (commit, T2), which denotes the commit of transaction T2.
10. The operation (start, T3) marks the start of transaction T3.
11. Finally, we see (write, T3, z, 7, 2), which represents a write operation by transaction T3 on variable z with the old value 7 and the new value 2.
Now, let's consider the crash scenario and the recovery process using undo and redo operations:
- When a crash occurs, the system needs to undo the incomplete transactions and redo the completed transactions after the last checkpoint.
- The undo list contains the transactions that need to be undone, i.e., the incomplete transactions after the last checkpoint. In this case, transactions T3 and T1 are the incomplete transactions after the checkpoint. Therefore, the undo list contains T3 and T1.
- The redo list contains the transactions that need to be redone, i.e., the completed transactions after the last checkpoint. In this case, transaction T2 is the only completed transaction after the checkpoint. Therefore, the redo list contains T2.
Hence, the correct answer is option A: Undo: T3, T1; Redo: T2.
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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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer?.
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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? for Computer Science Engineering (CSE) 2025 is part of Computer Science Engineering (CSE) preparation. The Question and answers have been prepared according to the Computer Science Engineering (CSE) exam syllabus. Information about 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? covers all topics & solutions for Computer Science Engineering (CSE) 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer?.
Solutions for 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? in English & in Hindi are available as part of our courses for Computer Science Engineering (CSE).
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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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer?, a detailed solution for 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? has been provided alongside types of 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? theory, EduRev gives you an
ample number of questions to practice 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);Q. 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 lista)Undo: T3, T1; Redo: T2b)Undo: T3, T1; Redo: T2, T4c)Undo: none; Redo: T2, T4, T3; T1d)Undo: T3, T1, T4; Redo: T2Correct answer is option 'A'. Can you explain this answer? tests, examples and also practice Computer Science Engineering (CSE) tests.
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