a. Example for using normal transaction undo mechanism : Consider a bank account S with balance $200. Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240. Now, when the transactions are executed in sequence T 1 , T 2 the log records would be as follows: < T 1 , S, 200, 220 > < T 2 , S, 220, 240 > Now, transaction T 1 needs to be undone...

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Answer 1

Expert Solution & Answer

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

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Answer 2

Expert Solution & Answer

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Expert Solution & Answer

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See solution

Answer 3

Expert Solution & Answer

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Expert Solution & Answer

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Check out a sample textbook solution

See solution

Answer 4

Expert Solution & Answer

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Expert Solution & Answer

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Check out a sample textbook solution

See solution

Answer 5

Expert Solution & Answer

Answer 6

Expert Solution & Answer

Answer 7

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Answer 8

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Answer 9

Chapter 19, Problem 11PE

Explanation of Solution

a.

Example for using normal transaction undo mechanism:

Consider a bank account S with balance $200.

Let two transactions individually deposit $20 in the account. Thus, the final balance should be $240.

Now, when the transactions are executed in sequence T₁, T₂ the log records would be as follows:
< T₁, S, 200, 220 >

< T₂, S, 220, 240 >

Now, transaction T₁ needs to be undone...

Answer 10

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Answer 11

Explanation of Solution

b.

Implementing point-in-time recovery using database dumps:

To modify the recovery algorithm from section 19.4 to implement point in time recovery using database dumps;

Identify the latest archival dump (say D) before the start of the erroneous transaction (say Te) that is < Te, start>.

Restore the database using this dump D.

Now, perform a redo of all log records starting from the dump till the transaction committed that is < Te, commit >.

Let S be the set of those transactions which were active at the commit time of Te.

Rollback all transactions in the set S including Te...

Answer 12

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Answer 13

Explanation of Solution

c.

Re-executing non-erroneous transactions logically:

To understand the reason the later non-erroneous transactions cannot be re-executed logically using log records, consider again the example from part (a);

Let both the transactions be undone and the balance be reverted back to $200.

Now, if T₂ needs to be redone while using the log record < T₂, ...

Answer 14

Expert Solution & Answer

Answer 15

Expert Solution & Answer

Answer 16

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Answer 17

Ch. 19 - Prob. 1PE Ch. 19 - Prob. 2PE Ch. 19 - Prob. 3PE Ch. 19 - Prob. 4PE Ch. 19 - Prob. 5PE Ch. 19 - Prob. 6PE Ch. 19 - Prob. 7PE Ch. 19 - Prob. 8PE Ch. 19 - Prob. 9PE Ch. 19 - Prob. 10PE

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Explanation of Solution

Explanation of Solution

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Chapter 19 Solutions