Recovery Manager Troubleshooting.docx

Recovery Manager Troubleshooting.docx

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RecoveryManagerTroubleshooting

TroubleshootingUser-ManagedMediaRecovery

Thischapterdescribeshowtotroubleshootuser-managedmediarecovery,andincludesthefollowingtopics:

∙AboutUser-ManagedMediaRecoveryProblems

∙InvestigatingtheMediaRecoveryProblem:

Phase1

∙TryingtoFixtheRecoveryProblemWithoutCorruptingBlocks:

Phase2

∙DecidingWhethertoAllowRecoverytoCorruptBlocks:

Phase3

∙AllowingRecoverytoCorruptBlocks:

Phase4

∙PerformingTrialRecovery

AboutUser-ManagedMediaRecoveryProblems

Table 20-1describespotentialproblemsthatcanoccurduringmediarecovery.

Table20-1MediaRecoveryProblems 

Problem

Description

Missingormisnamedarchivedlog

Recoverystopsbecausethedatabasecannotfindthearchivedlogrecordedinthecontrolfile.

Whenyouattempttoopenthedatabase,errorORA-1113indicatesthatadatafileneedsmediarecovery

Thiserrorcommonlyoccursbecause:

∙Youareperformingincompleterecoverybutfailedtorestoreallneededdatafilebackups.

∙IncompleterecoverystoppedbeforedatafilesreachedaconsistentSCN.

∙Youarerecoveringdatafilesfromanonlinebackup,butnotenoughredowasappliedtomakethedatafilesconsistent.

∙Youareperformingrecoverywithabackupcontrolfile,anddidnotspecifythelocationofaneededonlineredolog.

∙Adatafileisundergoingmediarecoverywhenyouattempttoopenthedatabase.

∙DatafilesneedingrecoverywerenotbroughtonlinebeforeexecutingRECOVERDATABASE,andsowerenotrecovered.

Redorecordproblems

Twopossiblecasesareasfollows:

∙Recoverystopsbecauseoffailedconsistencychecks,aproblemcalledstuckrecovery.Stuckrecoverycanoccurwhenanunderlyingoperatingsystemorstoragesystemlosesawriteissuedbythedatabaseduringnormaloperation.

∙Thedatabasesignalsaninternalerrorwhenapplyingtheredo.ThisproblemcanbecausedbyanOraclebug.Ifchecksumsarenotbeingused,itcanalsobecausedbycorruptionstotheredoordatablocks.

Corruptedarchivedlogs

Logsmaybecorruptedwhiletheyarestoredonorcopiedbetweenstoragesystems.IfDB_BLOCK_CHECKSUMisenabled,thenthedatabaseusuallysignalschecksumerrors.Ifchecksummingisnoton,thenlogcorruptionmayappearasaproblemwithredo.

Archivedlogswithincompatibleparallelredoformat

Ifyouenabletheparallelredofeature,thenthedatabasegeneratesredologsinanewformat.PriorreleasesofOracleareunabletoapplyparallelredologs.However,releasespriortoOracle9iRelease2（9.2）candetecttheparallelredoformatandindicatetheinconsistencywiththefollowingerrormessage:

Externalerror00303,00000,"cannotprocessParallelRedo".

SeeAlso:

OracleDatabasePerformanceTuningGuidetolearnabouttheparallelredofeature

Corrupteddatablocks

Adatafilebackupmayhavecontainedacorrupteddatablock,orthedatablockmaybecomecorruptedeitherduringrecoveryorwhenitwascopiedtothebackup.Ifchecksumsarebeingused,thenthedatabasesignalsachecksumerror.Otherwise,theproblemmayalsoappearasaredocorruption.

Randomproblems

Memorycorruptionsandothertransientproblemscanoccurduringrecovery.

Thesymptomsofmediarecoveryproblemsareusuallyexternalorinternalerrorssignaledduringrecovery.Forexample,anexternalerrorindicatesthataredoblockoradatablockhasfailedchecksumverificationchecks.Internalerrorscanbecausedbyeitherbugsinthedatabaseorerrorsarisingfromtheunderlyingoperatingsystemandhardware.

Ifmediarecoveryencountersaproblemwhilerecoveringadatabasebackup,whetheritisastuckrecoveryproblemoraproblemduringredoapplication,thedatabasealwaysstopsandleavesthedatafilesundergoingrecoveryinaconsistentstate,thatis,ataconsistentSCNprecedingthefailure.Youcanthendooneofthefollowing:

∙Openthedatabaseread-onlytoinvestigatetheproblem.

∙OpenthedatabasewiththeRESETLOGSoption,aslongastherequirementsforopeningRESETLOGShavebeenmet.NotethattheRESETLOGSrestrictionsapplytoopeningthestandbydatabaseaswell,becauseastandbydatabaseisupdatedbyaformofmediarecovery.

Ingeneral,openingthedatabaseread-onlyoropeningwiththeRESETLOGSoptionrequireallonlinedatafilestoberecoveredtothesameSCN.Ifthisrequirementisnotmet,thenthedatabasemaysignalORA-1113orothererrorswhenyouattempttoopen.SomecommoncausesofORA-1113aredescribedinTable 20-1.

Thebasicmethodologyforrespondingtomediarecoveryproblemsoccursinthefollowingphases:

1.Trytoidentifythecauseoftheproblem.Runatrialrecoveryifneeded.

2.Iftheproblemisrelatedtomissingredologsoryoususpectthereisaredolog,memory,ordatablockcorruption,thentrytoresolveitusingthemethodsdescribedinTable 20-2.

3.IfyoucannotresolvetheproblemusingthemethodsdescribedinTable 20-2,thendooneofthefollowing:

oOpenthedatabasewiththeRESETLOGSoptionifyouarerecoveringawholedatabasebackup.Ifyouhaveperformedserialmediarecovery,thenthedatabasecontainsallthechangesuptobutnotincludingthechangesattheSCNwherethecorruptionoccurred.NochangesfromthisSCNonwardareintherecoveredpartofthedatabase.Ifyouhaverestoredonlinebackups,thenopeningRESETLOGSsucceedsonlyifyouhaverecoveredthroughalltheALTER...ENDBACKUPoperationsintheredostream.

oProceedwithrecoverybyallowingmediarecoverytocorruptdatablocks.Aftermediarecoverycompletes,tryperformingblockmediarecoveryusingRMAN.

oCallOracleSupportServicesasalastresort.

SeeAlso:

"PerformingBlockMediaRecoverywithRMAN"tolearnaboutblockmediarecovery

InvestigatingtheMediaRecoveryProblem:

Phase1

Ifmediarecoveryencountersaproblem,thenobtainasmuchinformationaspossibleafterrecoveryhalts.Youdonotwanttowastetimefixingthewrongproblem,whichmayinfactmakemattersworse.

Thegoalofthisinitialinvestigationistodeterminewhethertheproblemiscausedbyincorrectsetup,corruptedredologs,corrupteddatablocks,memorycorruption,orotherproblems.Ifyouseeachecksumerroronadatablock,thenthedatablockiscorrupted.Ifyouseeachecksumerroronaredologblock,thentheredologiscorrupted.

Sometimesthecauseofarecoveryproblemcanbedifficulttodetermine.Nevertheless,themethodsinthischapterallowyoutoquicklyrecoveradatabaseevenwhenyoudonotcompletelyunderstandthecauseoftheproblem.

Toinvestigatemediarecoveryproblems:

1.Examinethealert.logtoseewhethertheerrormessagesgivegeneralinformationaboutthenatureoftheproblem.Forexample,doesthealert_SID.logindicateanychecksumfailures?

Doesthealert_SID.logindicatethatmediarecoverymayhavetocorruptdatablocksinordertocontinue?

2.CheckthetracefilegeneratedbytheOracleprocessduringrecovery.Itmaycontainadditionalerrorinformation.

TryingtoFixtheRecoveryProblemWithoutCorruptingBlocks:

Phase2

Dependingonthetypeofmediarecoveryproblemyoususpect,youhavedifferentsolutionsatyourdisposal.YoucantryoneoracombinationofthemethodsdescribedinTable 20-2.Notethatthesemethodsarefairlysafe:

inalmostallcases,theyshouldnotcauseanydamagetothedatabase.

Table20-2MediaRecoverySolutions 

Ifyoususpect...

Then...

Missing/misnamedarchivedlogs

Determinewhetheryouenteredthecorrectfilename.Ifyoudid,thenchecktoseewhetherthelogismissingfromtheoperatingsystem.Ifitismissing,andyouhaveabackup,thenrestorethebackupandapplythelog.Ifyoudonothaveabackup,thenifpossibleperformincompleterecoveryuptothepointofthemissinglog.

ORA-1113forALTERDATABASEOPEN

ReviewthecausesofthiserrorinTable 20-1.Makesurethatallread/writedatafilesrequiringrecoveryareonline.Ifyouuseabackupcontrolfileforrecovery,thenthecontrolfileanddatafilesmustbeataconsistentSCNforthedatabasetobeopened.Ifyoudonothavethenecessaryredo,thenyoumustre-createthecontrolfile.

Corruptarchivedlogs

Thelogiscorruptedifthechecksumverificationonthelogredoblockfails.IfDB_BLOCK_CHECKSUMisnotenabledeitherduringtherecoverysessionorwhenthedatabasegeneratedtheredo,thenrecoveryproblemsmaybecausedbycorruptedlogs.Ifthelogiscorruptandanalternatecopyofthecorruptlogisavailable,thentrytoapplyitandseewhetherthistacticfixestheproblem.

TheDB_BLOCK_CHECKSUMinitializationparameterdetermineswhetherchecksumsarecomputedforredologanddatablocks.

Archivedlogswithincompatibleparallelredoformat

IfyouarerunninganOraclereleasepriortoOracle9iRelease2,andifyouareattemptingtoapplyredologscreatedwiththeparallelredoformat,thenyoumustdothefollowingsteps:

1.Upgradethedatabasetoalaterrelease.

2.Performmediarecovery.

3.Shutdownthedatabaseconsistentlyandbackupthedatabase.

4.Downgradethedatabasetotheoriginalrelease.

SeeAlso:

OracleDatabasePerformanceTuningGuidetolearnabouttheparallelredofeature

Memorycorruptionortransientproblems

Youmaybeabletofixtheproblembyshuttingdownthedatabaseandrestartingrecovery.Thedatabseshouldbeleftinaconsistentstateifthesecondattemptalsofails.

Corruptdatablocks

Restoreandrecoverthedatafileagainwithuser-managedmethods,orrestoreandrecoverindividualdatablockswiththeRMANBLOCKRECOVERcommand.Thistacticmayfixtheproblem.

Adatablockiscorruptedifthechecksumverificationontheblockfails.IfDB_BLOCK_CHECKINGisdisabled,acorrupteddatablockproblemmayappearasaredoproblem.