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Based on the following System log at time of system crash, answer the questions that follows: [checkpoint]                    System Crash    What are the recovery actions in each of the following recovery techniques? Deferred Update Immediate update (Undo/Redo)

Based on the following System log at time of system crash, answer the questions that follows: [checkpoint]                    System Crash    What are the recovery actions in each of the following recovery techniques? Deferred Update Immediate update (Undo/Redo)

Database System Concepts
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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Based on the following System log at time of system crash, answer the questions that follows:

<start_transaction, T1>

<write_item, T1, B, 100, 200>

<commit, T1>

[checkpoint]

<start_transaction, T2>

<write_item, T2, C, 1500, 250>

<commit, T2>

<start_transaction, T3>

<write_item, T3, B, 200, 300>

<start_transaction, T4>

<write_item, T4, C, 1500, 250>

<write_item, T3, A, 500, 1000>

 

 

 

 

 

 

 

     System Crash

  

What are the recovery actions in each of the following recovery techniques?

  1. Deferred Update
  1. Immediate update (Undo/Redo)
<start transaction, T1> <write item, T1, B, 100, 200> <commit, T1> [checkpoint] <start transaction, T2> <write item, T2, C, 1500, 250> <commit, T2> <start transaction, T3> <write item, T3, B, 200, 300> <start transaction, T4> <write item, T4, C, 1500, 250> <write item, T3, A, 500, 1000> System Crash
Transcribed Image Text:<start transaction, T1> <write item, T1, B, 100, 200> <commit, T1> [checkpoint] <start transaction, T2> <write item, T2, C, 1500, 250> <commit, T2> <start transaction, T3> <write item, T3, B, 200, 300> <start transaction, T4> <write item, T4, C, 1500, 250> <write item, T3, A, 500, 1000> System Crash
Expert Solution
Step 1
start transaction, T
 
 
start transaction, 12]
start transaction, 12]start transaction, 12]
 
write item, Ti, A, 10, 20]
 
start transaction, Ta
 
write item, T2, B. 12, 25
 
write item, Ts, C, 21, 30]
 
commit. T
 
checkpoint]
 
write item, T2, D. 30, 35
 
commit, T2
 
write item, T3, A, 20, 30
 
start_transaction, T
 
write item, T₁, B, 25, 20
 
 
 
 
 
Step 2/2
Undo_item, T4, B, 25]
 
Abort_transaction, T4]
 
Undo_item, T3, A, 20]
 
Undo_item, T3, C, 21]
 
Abort_transaction, T3]
 
 
Final answer
Transactions T3 and T4 are undone,the compensation log records show that Transaction T2 is redone, since it has committed before the crash
 
 
Transaction T1 is committed before checkpoint and hence all changes related to T1 are
 
already written to the disk,thus T1 is neither undone nor redone.
 
Transactions T3 and T4 are rolled back
 
The compensation log record(red color text) corresponds to write_item operations for
 
T3 and T4 these are undone.
 
-System crash
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