Consider a system where the log contains the following records (in order):
⟨T1 start⟩
⟨T1, X, 10, 20⟩
⟨T2 start⟩
⟨checkpoint {T1, T2}⟩
⟨T2, Y, 30, 40⟩
(crash)
Which of the following is true immediately after the crash, under recovery with WAL?

Question

Consider a system where the log contains the following records (in order): 
 ⟨T1 start⟩   
 ⟨T1, X, 10, 20⟩   
 ⟨T2 start⟩   
 ⟨checkpoint {T1, T2}⟩   
 ⟨T2, Y, 30, 40⟩   
 (crash) 
 Which of the following is true immediately after the crash, under recovery with WAL?

Accepted Answer

Both T1 and T2 updates must be undone.

Answer

Both T1 and T2 updates must be redone.

Answer

Only T1’s update must be redone; T2’s must be undone.

Answer

T1’s update must be undone; T2’s update must be redone.

Crowdly

Consider a system where the log contains the following records (in order): ⟨T1...

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