hw5-handout

hw5-handout - 11/23/09 Homework5 CS143Fall2009

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Unformatted text preview: 11/23/09 Homework5 CS143Fall2009 ProblemI:Considerthefollowingschedule:involving transacDonsT1,T2,T3,T4performingthefollowing sequenceofacDons(w3(A)meansthatT3performs write(A),c2meansthatT2commits,etc.) w3(A)r1(A)c3w1(B)c1r2(B)w2(C)r4(B)c4c2 (a) Isitaserialschedule? (b) Isthescheduleconflictserializable?Ifso,whatareall theequivalentserialschedules? (c) Istheschedulerecoverable? (d) Istheschedulecascadeless?Ifnot,canwemakeit cascadelessbymovingasinglecommitoperaDontoa differentposiDon? 1 11/23/09 Recoverability Anunrecoverable schedule: Toberecoverable,transacDonsmustwaitandcommitonly aSeralltransacDonswhosechangestheyreadcommit: Avoidcascadingaborts(rollbacks) ThefollowingscheduleforFavoidsthesituaDonF2 AscheduleisstrictifforanytwotransacDonsT1,T2,ifawrite operaDonofT1precedesaconflicDngoperaDonofT2(either readorwrite),thenthecommiteventofT1alsoprecedes thatconflicDngoperaDonofT2. Anystrictscheduleiscascadeless,andexpeditesrecoveryfrom failures 2 11/23/09 RealaDonsBetweenSchedules Serial Serial conflictserializable viewserializable allschedules strict cascadless recoverable allschedules MoreProblems 16.28:IsstarvaDonsDllpossibleusingdeadlock avoidancescheme? 3 ...
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This note was uploaded on 04/28/2010 for the course CS 143 taught by Professor Zaniolo during the Fall '01 term at UCLA.

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