AtomicityConcurrencyAtomicityRecoverabilityModelModelCommit pointGeneralizeMIT OpenCourseWarehttp://ocw.mit.edu 6.033 Computer System Engineering Spring 2009 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.AtomicityFailures: 1) Replicate + vote2) RecoverabilityNo “partial” stateM1M2xfer (from, to, $ amount)“All or nothing”RECOVERABILITYConcurrencyS = 1000xfer (S, C, 100) : A1xfer (S, C, 200) : A2A1 before A2ORA2 before A1ISOLATIONAtomicity- Hide compositeness of actions- REC + ISO- Consistency Æ Invariant- DurabilityRecoverability-Fail-fast- Repair (recover)-Restarts1) Recoverable sector2) Version history3) LogsModel- No concurrency- No hardware errors- Software errorsAppOS BufferModelcareful_put (sec, data)” _getD0D1chooser0Solution: CopyGolden Rule:Never modify only copy.Commit point- Before Î not visible- After Î
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