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Unformatted text preview: Crash Recovery 181 10 20 30 40 50 60 00 end_checkpoint begin_checkpoint LOG LSN update: T1 writes P5 update: T2 writes P3 update: T3 writes P3 CRASH, RESTART T2 end T2 commit T1 abort 70 Figure 18.1 Execution with a Crash (b) The dirty pages in the buffer pool at the time of the crash. (c) Transactions that were active at the time of the crash which need to be undone. The Redo phase follows Analysis and redoes all changes to any page that might have been dirty at the time of the crash. The Undo phase follows Redo and undoes the changes of all transactions that were active at the time of the crash. 2. (a) For this example, we will assume that the Dirty Page Table and Transaction Table were empty before the start of the log. Analysis determines that the last begin checkpoint was at LSN 00 and starts at the corresponding end checkpoint (LSN 10). We will denote Transaction Table records as (transID, lastLSN) and Dirty Page Table records as (pageID, recLSN) sets....
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- Fall '12