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?

Answer

Both T1 and T2 updates must be redone.

Answer

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

Answer

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

Answer

Both T1 and T2 updates must be undone.

Crowdly

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

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