Data Mgmt Lab_Part_63 - Crash Recovery 187 10 20 30 40 LSN...

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Unformatted text preview: Crash Recovery 187 10 20 30 40 LSN LOG 00 begin_checkpoint update: T1 writes P1 update: T2 writes P2 50 60 70 80 T1 commit CRASH, RESTART T3 commit end_checkpoint update: T3 writes P3 T2 abort T1 end Figure 18.4 Log Records between Checkpoint Records Answer 18.9 The answer to each question is given below. 1. In ARIES, first a begin checkpoint record is written and then, after some time, an end checkpoint record is written. While the end checkpoint record is being constructed, the DBMS continues executing transactions and writing other log records. So, we could have log records between the begin checkpoint and the end checkpoint records. The only guarantee we have is that the transaction table and the dirty page table are accurate as of the time of the begin checkpoint record. 2. The Analysis phase begins by examining the most recent begin checkpoint log record and then searches for the next end checkpoint record. Then the Dirty Page Table and the Transaction Table are initialized to the copies of those struc-...
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Data Mgmt Lab_Part_63 - Crash Recovery 187 10 20 30 40 LSN...

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