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2. Assume the system use write-ahead logging. The initial value of A, B, and C is 10, 0 and 0. Please take a look at the following log record. (1) What are the values of A, B, C after the crash recovery? (2) Does the system use strict 2PL to manage its transactions? Why? Log ID Transaction ID Action 100 1 UPDATE; A=10; A=5 101 1 UPDATE; B=0; B=20 102 2 BEGIN 103 1 СОMMIT 104 2 UPDATE; B=20; B=25 105 2 UPDATE; A=5; A=15 106 BEGIN 107 UPDATE; C=0; C=30 108 2 COMMIT 109 3 UPDATE B=25; B=30 CRASH. 3.

2. Assume the system use write-ahead logging. The initial value of A, B, and C is 10, 0 and 0. Please take a look at the following log record. (1) What are the values of A, B, C after the crash recovery? (2) Does the system use strict 2PL to manage its transactions? Why? Log ID Transaction ID Action 100 1 UPDATE; A=10; A=5 101 1 UPDATE; B=0; B=20 102 2 BEGIN 103 1 СОMMIT 104 2 UPDATE; B=20; B=25 105 2 UPDATE; A=5; A=15 106 BEGIN 107 UPDATE; C=0; C=30 108 2 COMMIT 109 3 UPDATE B=25; B=30 CRASH. 3.

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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### Write-Ahead Logging (WAL) and Crash Recovery: An Educational Guide This guide helps you understand how write-ahead logging (WAL) helps in crash recovery within database systems. Consider the following log record: --- #### Initial Values - **A = 10** - **B = 0** - **C = 0** --- #### Log Record Entries | Log ID | Transaction ID | Action | |--------|-----------------|---------------------------| | 100 | 1 | UPDATE; A=10; A=5 | | 101 | 1 | UPDATE; B=0; B=20 | | 102 | 2 | BEGIN | | 103 | 1 | COMMIT | | 104 | 2 | UPDATE; B=20; B=25 | | 105 | 2 | UPDATE; A=5; A=15 | | 106 | 3 | BEGIN | | 107 | 3 | UPDATE; C=0; C=30 | | 108 | 2 | COMMIT | | 109 | 3 | UPDATE; B=25; B=30 | | --- | --- | CRASH………………………………….. | --- ### Questions and Answers #### (1) What are the values of A, B, and C after the crash recovery? To determine the values of A, B, and C after crash recovery, follow these steps: - **Transaction 1**: This transaction starts at Log ID 100 and commits at Log ID 103. - Updates A from 10 to 5. - Updates B from 0 to 20. - **Committed**, thus changes are reflected in the database state. - **Transaction 2**: This transaction starts at Log ID 102 and commits at Log ID 108. - Updates B from 20 to 25. - Updates A from 5 to 15. - **Committed**, thus changes are also reflected in the database state. - **Transaction 3**: This transaction starts at Log ID 106 but doesn't commit before the crash. - Updates C from 0 to 30. - Updates B from 25 to 30 (not committed). Since write-ahead logging involves making sure that changes
Transcribed Image Text:### Write-Ahead Logging (WAL) and Crash Recovery: An Educational Guide This guide helps you understand how write-ahead logging (WAL) helps in crash recovery within database systems. Consider the following log record: --- #### Initial Values - **A = 10** - **B = 0** - **C = 0** --- #### Log Record Entries | Log ID | Transaction ID | Action | |--------|-----------------|---------------------------| | 100 | 1 | UPDATE; A=10; A=5 | | 101 | 1 | UPDATE; B=0; B=20 | | 102 | 2 | BEGIN | | 103 | 1 | COMMIT | | 104 | 2 | UPDATE; B=20; B=25 | | 105 | 2 | UPDATE; A=5; A=15 | | 106 | 3 | BEGIN | | 107 | 3 | UPDATE; C=0; C=30 | | 108 | 2 | COMMIT | | 109 | 3 | UPDATE; B=25; B=30 | | --- | --- | CRASH………………………………….. | --- ### Questions and Answers #### (1) What are the values of A, B, and C after the crash recovery? To determine the values of A, B, and C after crash recovery, follow these steps: - **Transaction 1**: This transaction starts at Log ID 100 and commits at Log ID 103. - Updates A from 10 to 5. - Updates B from 0 to 20. - **Committed**, thus changes are reflected in the database state. - **Transaction 2**: This transaction starts at Log ID 102 and commits at Log ID 108. - Updates B from 20 to 25. - Updates A from 5 to 15. - **Committed**, thus changes are also reflected in the database state. - **Transaction 3**: This transaction starts at Log ID 106 but doesn't commit before the crash. - Updates C from 0 to 30. - Updates B from 25 to 30 (not committed). Since write-ahead logging involves making sure that changes
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