Data Mgmt Lab_Part_62 - 184 Chapter 18 LSN LSN LSN LSN LSN...

184 Chapter 18
LSN 20 Add (T1,20) to TT and (P1,20) to DPT
LSN 30 Add (T2,30) to TT and (P2,30) to DPT
LSN 40 Add (T3,40) to TT and (P3,40) to DPT
LSN 50 Change status of T2 to C
LSN 60 Change (T3,40) to (T3,60)
LSN 70 Remove T2 from TT
LSN 80 Change (T1,20) to (T1,70) and add (P5,70) to DPT
LSN 90 No action
At the end of analysis, the transaction table contains the following entries: (T1,80),
and (T3,60). The Dirty Page Table has the following entries: (P1,20), (P2,30),
(P3,40), and (P5,80).
3. Redo starts from LSN20 (minimum recLSN in DPT).
LSN 20 Check whether P1 has pageLSN more than 10 or not. Since it is a
committed transaction, we probably need not redo this update.
LSN 30 Redo the change in P2
LSN 40 Redo the change in P3
LSN 50 No action
LSN 60 Redo the changes on P2
LSN 70 No action
LSN 80 Redo the changes on P5
LSN 90 No action
4. ToUndo consists of (80, 60).
LSN 80 Undo the changes in P5. Append a CLR: Undo T1 LSN 80, set
undonextLSN = 20. Add 20 to ToUndo.
ToUndo consists of (60, 20).
LSN 60 Undo the changes on P2. Append a CLR: Undo T3 LSN 60, set
undonextLSN = 40. Add 40 to ToUndo.
ToUndo consists of (40, 20).
LSN 40 Undo the changes on P3. Append a CLR: Undo T3 LSN 40, T3
end
ToUndo consists of (20).