Advanced UserManaged Recovery Scenarios.docx
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Advanced UserManaged Recovery Scenarios.docx
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AdvancedUserManagedRecoveryScenarios
AdvancedUser-ManagedRecoveryScenarios
Thischapterdescribeshowtorecoverfromcommonmediafailures,andincludesthefollowingtopics:
∙RecoveringAftertheLossofDatafiles:
Scenarios
∙RecoveringThroughanAddedDatafilewithaBackupControlFile:
Scenario
∙Re-CreatingDatafilesWhenBackupsAreUnavailable:
Scenario
∙RecoveringThroughRESETLOGSwithCreatedControlFile:
Scenario
∙RecoveringNOLOGGINGTablesandIndexes:
Scenario
∙RecoveringRead-OnlyTablespaceswithaBackupControlFile:
Scenario
∙RecoveringTransportableTablespaces:
Scenario
∙RecoveringAftertheLossofOnlineRedoLogFiles:
Scenarios
∙RecoveringAftertheLossofArchivedRedoLogFiles:
Scenario
∙RecoveringfromaDroppedTable:
Scenario
∙PerformingMediaRecoveryinaDistributedEnvironment:
Scenario
∙DroppingaDatabasewithSQL*Plus
RecoveringAftertheLossofDatafiles:
Scenarios
Ifamediafailureaffectsdatafiles,thentherecoveryproceduredependson:
∙Thearchivingmodeofthedatabase:
ARCHIVELOGorNOARCHIVELOG
∙Thetypeofmediafailure
∙Thefilesaffectedbythemediafailure
LosingDatafilesinNOARCHIVELOGMode
IfeitherapermanentortemporarymediafailureaffectsanydatafilesofadatabaseoperatinginNOARCHIVELOGmode,thenthedatabaseautomaticallyshutsdown.
Ifthemediafailureistemporary,correcttheunderlyingproblemandrestartthedatabase.Usually,crashrecoverywillrecoverallcommittedtransactionsfromtheonlineredolog.Ifthemediafailureispermanent,thenrestorethedatabaseasdescribedin"RecoveringaDatabaseinNOARCHIVELOGMode".
LosingDatafilesinARCHIVELOGMode
IfeitherapermanentortemporarymediafailureaffectsthedatafilesofadatabaseoperatinginARCHIVELOGmode,thenthefollowingscenarioscanoccur.
DamagedDatafiles
DatabaseStatus
Solution
DatafilesintheSYSTEMtablespaceordatafileswithactiveundosegments.
Databaseshutsdown.
Ifthehardwareproblemistemporary,thenfixitandrestartthedatabase.Usually,crashrecoveryrecoverslosttransactions.Ifthehardwareproblemispermanent,thenrecoverthedatabaseasdescribedin"PerformingClosedDatabaseRecovery".
DatafilesnotintheSYSTEMtablespaceordatafilesthatdonotcontainactiverollbackorundosegments.
Affecteddatafilesaretakenoffline,butthedatabasestaysopen.
Iftheunaffectedportionsofthedatabasemustremainavailable,thendonotshutdownthedatabase.Taketablespacescontainingproblemdatafilesofflineusingthetemporaryoption,thenrecoverthemasdescribedin"PerformingDatafileRecoveryinanOpenDatabase".
RecoveringThroughanAddedDatafilewithaBackupControlFile:
Scenario
IfdatabaserecoverywithabackupcontrolfilerollsforwardthroughaCREATETABLESPACEoranALTERTABLESPACEADDDATAFILEoperation,thenthedatabasestopsrecoverywhenapplyingtheredorecordfortheaddedfilesandletsyouconfirmthefilenames.
Forexample,supposethefollowingsequenceofeventsoccurs:
1.Youbackupthedatabase
2.Youcreateanewtablespacecontainingtwodatafiles:
/oracle/oradata/trgt/test01.dbfand/oracle/oradata/trgt/test02.dbf.
3.YoulaterrestoreabackupcontrolfileandperformmediarecoverythroughtheCREATETABLESPACEoperation.
YoumayseethefollowingerrorwhenapplyingtheCREATETABLESPACEredodata:
ORA-00283:
recoverysessioncanceledduetoerrors
ORA-01244:
unnameddatafile(s)addedtocontrolfilebymediarecovery
ORA-01110:
datafile11:
'/oracle/oradata/trgt/test02.dbf'
ORA-01110:
datafile10:
'/oracle/oradata/trgt/test01.dbf'
TorecoverthroughanADDDATAFILEoperation:
1.ViewthefilesaddedbyselectingfromV$DATAFILE.Forexample:
2.SELECTFILE#,NAME
3.FROMV$DATAFILE;
4.
5.FILE#NAME
6.-------------------------------------
7.1/oracle/oradata/trgt/system01.dbf
8..
9..
10..
11.10/oracle/oradata/trgt/UNNAMED00001
12.11/oracle/oradata/trgt/UNNAMED00002
13.
14.Ifmultipleunnamedfilesexist,thendeterminewhichunnamedfilecorrespondstowhichdatafilebyusingoneofthesemethods:
∙Openthealert_SID.log,whichcontainsmessagesabouttheoriginalfilelocationforeachunnamedfile.
∙DerivetheoriginalfilelocationofeachunnamedfilefromtheerrormessageandV$DATAFILE:
eachunnamedfilecorrespondstothefileintheerrormessagewiththesamefilenumber.
IssuetheALTERDATABASERENAMEFILEstatementtorenamethedatafiles.Forexample,enter:
ALTERDATABASERENAMEFILE'/db/UNNAMED00001'TO
'/oracle/oradata/trgt/test01.dbf';
ALTERDATABASERENAMEFILE'/db/UNNAMED00002'TO
'/oracle/oradata/trgt/test02.dbf';
Continuerecoverybyissuingthepreviousrecoverystatement.Forexample:
RECOVERAUTOMATICDATABASEUSINGBACKUPCONTROLFILEUNTILCANCEL
Re-CreatingDatafilesWhenBackupsAreUnavailable:
Scenario
Ifadatafileisdamagedandnobackupofthefileisavailable,thenyoucanstillrecoverthedatafileif:
∙Allarchivedlogfileswrittenafterthecreationoftheoriginaldatafileareavailable
∙Thecontrolfilecontainsthenameofthedamagedfile(thatis,thecontrolfileiscurrent,orisabackuptakenafterthedamageddatafilewasaddedtothedatabase)
Note:
Youcannotre-createanyofthedatafilesfortheSYSTEMtablespacebyusingtheCREATEDATAFILEclauseoftheALTERDATABASEstatementbecausethenecessaryredoisnotavailable.
Tore-createadatafileforrecovery:
1.Createanew,emptydatafiletoreplaceadamageddatafilethathasnocorrespondingbackup.Forexample,assumethatthedatafile?
/oradata/trgt/users01.dbfhasbeendamaged,andnobackupisavailable.Thefollowingstatementre-createstheoriginaldatafile(samesize)ondisk2:
2.ALTERDATABASECREATEDATAFILE'?
/oradata/trgt/users01.dbf'AS
3.'/disk2/users01.dbf';
4.
Thisstatementcreatesanemptyfilethatisthesamesizeasthelostfile.Thedatabaselooksatinformationinthecontrolfileandthedatadictionarytoobtainsizeinformation.Theolddatafileisrenamedasthenewdatafile.
5.Performmediarecoveryontheemptydatafile.Forexample,enter:
6.RECOVERDATAFILE'/disk2/users01.dbf'
7.
8.Allarchivedlogswrittenaftertheoriginaldatafilewascreatedmustbeappliedtothenew,emptyversionofthelostdatafileduringrecovery.
RecoveringThroughRESETLOGSwithCreatedControlFile:
Scenario
YoucanrecoverbackupsthroughanOPENRESETLOGSsolongas:
∙Youhaveacurrent,backup,orcreatedcontrolfilethatknowsaboutthepriorincarnations
∙Youhaveallavailablearchivedredologs
Ifyouneedtore-createthecontrolfile,thetracefilegeneratedbyALTERDATABASEBACKUPCONTROLFILETOTRACEwillcontainthenecessarycommandstore-constructthecompleteincarnationhistory.TheV$DATABASE_INCARNATIONviewdisplaystheRESETLOGShistoryknowntothecontrolfile,whiletheV$LOG_HISTORYviewdisplaysthearchivedloghistory.
Itispossiblefortheincarnationhistorytobeincompleteintheinre-createdcontrolfile.Forexample,archivedlogsnecessaryforrecoverymaybemissing.Inthiscase,itispossibletocreateincarnationrecordsexplicitlywiththeALTERDATABASEREGISTERLOGFILEstatement.
Inthefollowingexample,youregisterfourlogsthatarenecessaryforrecoverybutarenotrecordedinthere-createdcontrolfile,andthenrecoverthedatabase:
ALTERDATABASEREGISTERLOGFILE'?
/oradata/trgt/arch/arcr_1_1_42343523.arc';
ALTERDATABASEREGISTERLOGFILE'?
/oradata/trgt/arch/arcr_1_1_34546466.arc';
ALTERDATABASEREGISTERLOGFILE'?
/oradata/trgt/arch/arcr_1_1_23435466.arc';
ALTERDATABASEREGISTERLOGFILE'?
/oradata/trgt/arch/arcr_1_1_12343533.arc';
RECOVERAUTOMATICDATABASE;
RecoveringNOLOGGINGTablesandIndexes:
Scenario
YoucancreatetablesandindexeswiththeCREATETABLEASSELECTstatement.YoucanalsospecifythatthedatabasecreatethemwiththeNOLOGGINGoption.WhenyoucreateatableorindexasNOLOGGING,thedatabasedoesnotgenerateredologrecordsfortheoperation.Thus,youcannotrecoverobjectscreatedwithNOLOGGING,evenifyouarerunninginARCHIVELOGmode.
Note:
IfyoucannotaffordtolosetablesorindexescreatedwithNOLOGGING,thenmakeabackupaftertheunrecoverabletableorindexiscreated.
Beawarethatwhenyouperformmediarecovery,andsometablesorindexesarecreatednormallywhereasothersarecreatedwiththeNOLOGGINGoption,theNOLOGGINGobjectsaremarkedlogicallycorruptbytheRECOVERoperation.AnyattempttoaccesstheunrecoverableobjectsreturnsanORA-01578errormessage.DroptheNOLOGGINGobjectsandre-createthemifneeded.
BecauseitispossibletocreateatablewiththeNOLOGGINGoptionandthencreateanindexwiththeLOGGINGoptiononthattable,theindexisnotmarkedaslogicallycorruptafteryouperformmediarecovery.Thetablewasunrecoverable(andthusmarkedascorruptafterrecovery),however,sotheindexpointstocorruptblocks.Theindexmustbedropped,andthetableandindexmustbere-createdifnecessary.
SeeAlso:
OracleDataGuardConceptsandAdministrationforinformationabouttheimpactofNOLOGGINGonabdatabase
RecoveringRead-OnlyTablespaceswithaBackupControlFile:
Scenario
Ifyouhavearead-onlytablespaceonread-onlyorslowmedia,thenyoumayencountererrorsorpoorperformancewhenrecoveringwiththeUSINGBACKUPCONTROLFILEoption.Thissituationoccurswhenthebackupcontrolfileindicatesthatatablespacewasread/writewhenthecontrolfilewasbackedup.Inthiscase,mediarecoverymayattempttowritetothefiles.Forread-onlymedia,thedatabaseissuesanerrorsayingthatitcannotwritetothefiles.Forslowmedia,suchasahierarchicalstoragesystembackedupbytapes,performancemays
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