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Question 4: Write-ahead Log (15) Consider the following portion of a write-ahead log. In this log, UPDATE records are of
Posted: Sun May 15, 2022 10:14 am
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- Question 4 Write Ahead Log 15 Consider The Following Portion Of A Write Ahead Log In This Log Update Records Are Of 1 (158.48 KiB) Viewed 55 times
Question 4: Write-ahead Log (15) Consider the following portion of a write-ahead log. In this log, UPDATE records are of the form UPDATE <var>=<old value>; <var>=<new value> Log ID The system crashed after log ID 114; no further entries were written. 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=30 110 4 BEGIN 4 UPDATE; C=30; C=40 112 3 UPDATE; A=15; A=45 113 3 COMMIT 114 4 UPDATE; A=45; A=50 CRASH... 111 1. After recovery, what are the values of A, B and C? If it is impossible to determine the value for any of these variables, write “None" in the corresponding parameter. Please explain your answer. 2. Is log portion shown above consistent with a transaction processing system that is using two-phase locking? Explain your answer.