Learning objectives
What you will be able to explain
- What is the correct order of ARIES restart phases after a crash?
- Which structures/outcomes are produced from the Analysis phase?
- ARIES Analysis Pass: complete the Transaction Table and Dirty Page Table
- From the same scenario, which transactions are Winners and Losers at crash time?
- What is the Redo start LSN for this restart?
- ARIES Redo Pass: mark each UPDATE as Redo or Ignore
Section 01
What is the correct order of ARIES restart phases after a crash? to ARIES Analysis Pass: complete the Transaction Table and Dirty Page Table
01
What is the correct order of ARIES restart phases after a crash?
ARIES restart first reconstructs state (Analysis), then repeats history (Redo), then rolls back loser transactions (Undo).
02
Which structures/outcomes are produced from the Analysis phase?
Analysis reconstructs transaction/page state at crash and identifies winner/loser transactions. It does not rebuild physical index layout.
03
ARIES Analysis Pass: complete the Transaction Table and Dirty Page Table
After scanning forward from the checkpoint: T2 commits and ends (removed), T1 and T3 remain active with lastLSN 120 and 130. DPT keeps first-dirty LSNs: P5=30, P7=40, then adds P9=100 and P8=120.
Guided checkpoint
Use the following log and checkpoint snapshot.
| LSN | TID | prevLSN | ACTION |
|---|---|---|---|
| 10 | T1 | BEGIN | |
| 20 | T2 | BEGIN | |
| 30 | T1 | 10 | UPDATE P5 |
| 40 | T2 | 20 | UPDATE P7 |
| 50 | T1 | 30 | UPDATE P7 |
| 60 | BEGIN_CHECKPOINT | ||
| 70 | T2 | 40 | COMMIT |
| 80 | T2 | 70 | END |
| 90 | T3 | BEGIN | |
| 100 | T3 | 90 | UPDATE P9 |
| 110 | END_CHECKPOINT | ||
| 120 | T1 | 50 | UPDATE P8 |
| 130 | T3 | 100 | UPDATE P7 |
Restart begins at the checkpoint (LSN 60). The checkpoint state loaded at restart is:
Transaction table (initial)
| TID | lastLSN |
|---|---|
| T1 | 50 |
| T2 | 40 |
Dirty page table (initial)
| PID | recLSN |
|---|---|
| P5 | 30 |
| P7 | 40 |
Fill the final tables after Analysis. Choose "No Entry" where applicable.
Section 02
From the same scenario, which transactions are Winners and Losers at crash time? to ARIES Redo Pass: mark each UPDATE as Redo or Ignore
01
From the same scenario, which transactions are Winners and Losers at crash time?
T2 has COMMIT and END before crash, so it is a winner. T1 and T3 have no commit record, so they are losers.
02
What is the Redo start LSN for this restart?
Redo starts from the minimum recLSN in the Dirty Page Table. Here, min{30, 40, 100, 120} = 30.
Guided checkpoint
Use the post-analysis DPT from q3.
03
ARIES Redo Pass: mark each UPDATE as Redo or Ignore
Redo starts at the minimum recLSN, which is 30. All listed UPDATE records are on pages in the DPT with recLSN <= record LSN, and the question assumes pageLSN < LSN for all shown records. Therefore every listed UPDATE is redone: 30, 40, 50, 100, 120, and 130.
Guided checkpoint
Dirty page table (after analysis)
| PID | recLSN |
|---|---|
| P5 | 30 |
| P7 | 40 |
| P8 | 120 |
| P9 | 100 |
Apply ARIES redo checks (repeat history). Assume pageLSN is always less than LSN for the shown records.
Section 03
About ARIES Redo rules: to ARIES Undo Pass: mark each UPDATE as Undo or Ignore
01
About ARIES Redo rules:
ARIES redo repeats history but uses DPT/pageLSN checks to skip unnecessary work. It is not restricted to winners only.
02
Undo initialization: which LSN is processed first?
Undo uses a max-priority strategy on ToUndo, so it starts from the largest LSN among losers.
Guided checkpoint
| Loser TID | lastLSN |
|---|---|
| T1 | 120 |
| T3 | 130 |
03
ARIES Undo Pass: mark each UPDATE as Undo or Ignore
T2 is committed (winner), so its updates are ignored in Undo. All listed updates by loser transactions T1 and T3 are undone.
Guided checkpoint
| Winners | Losers |
|---|---|
| {T2} | {T1, T3} |
Undo only processes loser transactions backward via prevLSN chains.
Section 04
How many CLRs are generated during Undo in this scenario? to Why can Redo reapply updates from loser transactions even though they will be undone later?
01
How many CLRs are generated during Undo in this scenario?
Loser UPDATEs undone are at LSN 130, 120, 100, 50, and 30. That yields 5 CLRs.
Guided checkpoint
Assume each undone UPDATE generates exactly one CLR.
02
When Undo reaches a loser's BEGIN record, what is the next ARIES action?
After all undoable records are processed and BEGIN is reached, ARIES finalizes the transaction with END and removes it from tracking.
03
Why can Redo reapply updates from loser transactions even though they will be undone later?
ARIES first reconstructs the exact pre-crash state via Redo (repeat history), then removes uncommitted effects via Undo.
Knowledge check
Turn understanding into recall.
The quiz now follows the same concepts in scored form. You can return to this lesson from the quiz whenever a gap appears.