## ARIES algorithm

ARIES algorithm. ARIES algorithm. Consider the recovery scenario described in the following, in which we use the ARIES recovery

algorithm. At the beginning of time, there are no transactions active in the system and no dirty pages. A
checkpoint is taken. After that, three transactions, T1, T2, and T3, enter the system and perform various
operations. The system experiences a crash, and during recovery, the system experiences another crash.
The detailed log follows:
LOG
LSN PREV_LSN TRAN_ID TYPE PAGE_ID
— ——– ——- —– ——–
1 – – begin CKPT –
2 – – end CKPT –
3 NULL T1 update P5
4 NULL T2 update P2
5 NULL T3 update P7
6 5 T3 update P5
7 3 T1 update P7
8 4 T2 update P3
9 7 T1 commit –
10 6 T3 abort –
11 9 T1 end –
——– XXXXXXX — FIRST CRASH! — XXXXXXX ——–
12 8 T2 abort –
13 12 T2 CLR P3 (undonextLSN=4)
——– XXXXXXX — SECOND CRASH! — XXXXXXX ——–
The log ends right after the second crash, before the second recovery procedure is initiated. Considering
again that the system employs the ARIES recovery algorithm, answer the following questions.

The log ends right after the second crash, before the second recovery procedure is initiated. Considering
again that the system employs the ARIES recovery algorithm, answer the following questions.
1. What is the state of the transaction table after the analysis phase in the recovery from the first
crash? What is the state of the transaction table after the analysis phase in the recovery from the
second crash? Explain how these states differ and why.
2. What is the state of the dirty page table after the analysis phase in the recovery from the first
crash? What is the state of the dirty page table after the analysis phase in the recovery from the
second crash? Explain how these states differ and why.
3. At what LSN does redo start in the recovery from the first crash? What about in the recovery
from the second crash? Explain how these LSNs differ and why.
4. In the scenario, the redo phase in the recovery from the first crash completes. Can we say which
updates will cause actual writes to data pages in the redo phase of the recovery from the second
crash? Explain why or why not.
5. Show the additional contents of the log after the recovery procedure completes after the second
crash. Provide a brief explanation for why any new log records shown need to be added.

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