Checkpointing (cont)
Recovery: scan backwards through log file processing as before.
Determining where to stop depends on ...
- whether we meet
<ENDCHKPT> or <CHKPT...> first
If we encounter <ENDCHKPT> first:
- we know that all incomplete tx's come after prev
<CHKPT...>
- thus, can stop backward scan when we reach
<CHKPT...>
If we encounter <CHKPT (T1,..,Tk)> first:
- crash occurred during the checkpoint period
- any of
T1,..,Tk that committed before crash are ok
- for uncommitted tx's, need to continue backward scan
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