15Backup and Recovery.docx
- 文档编号:7580337
- 上传时间:2023-01-25
- 格式:DOCX
- 页数:21
- 大小:72.49KB
15Backup and Recovery.docx
《15Backup and Recovery.docx》由会员分享,可在线阅读,更多相关《15Backup and Recovery.docx(21页珍藏版)》请在冰豆网上搜索。
15BackupandRecovery
15BackupandRecovery
Backupandrecoveryproceduresprotectyourdatabaseagainstdatalossandreconstructthedata,shouldlossoccur.Thereconstructingofdataisachievedthroughmediarecovery,whichreferstothevariousoperationsinvolvedinrestoring,rollingforward,androllingbackabackupofdatabasefiles.Thischapterintroducesconceptsfundamentaltodesigningabackupandrecoverystrategy.
Thischaptercontainsthefollowingtopics:
∙IntroductiontoBackup
∙IntroductiontoRecovery
∙DecidingWhichRecoveryTechniquetoUse
∙FlashRecoveryArea
SeeAlso:
∙"OverviewofDatabaseBackupandRecoveryFeatures"
∙OracleDatabaseBackupandRecoveryBasics
∙OracleDatabaseBackupandRecoveryAdvancedUser'sGuide
IntroductiontoBackup
Abackupisacopyofdata.Thiscopycanincludeimportantpartsofthedatabase,suchasthecontrolfileanddatafiles.Abackupisasafeguardagainstunexpecteddatalossandapplicationerrors.Ifyoulosetheoriginaldata,thenyoucanreconstructitbyusingabackup.
Backupsaredividedintophysicalbackupsandlogicalbackups.Physicalbackups,whicharetheprimaryconcerninabackupandrecoverystrategy,arecopiesofphysicaldatabasefiles.YoucanmakephysicalbackupswitheithertheRecoveryManager(RMAN)utilityoroperatingsystemutilities.Incontrast,logicalbackupscontainlogicaldata(forexample,tablesandstoredprocedures)extractedwithanOracleutilityandstoredinabinaryfile.Youcanuselogicalbackupstosupplementphysicalbackups.
TherearetwowaystoperformOraclebackupandrecovery:
RecoveryManageranduser-managedbackupandrecovery.
RecoveryManager(RMAN)isanOracleutilitythatcanbackup,restore,andrecoverdatabasefiles.ItisafeatureoftheOracledatabaseserveranddoesnotrequireseparateinstallation.
YoucanalsouseoperatingsystemcommandsforbackupsandSQL*Plusforrecovery.Thismethod,alsocalleduser-managedbackupandrecovery,isfullysupportedbyOracle,althoughuseofRMANishighlyrecommendedbecauseitismorerobustandgreatlysimplifiesadministration.
WhetheryouuseRMANoruser-managedmethods,youcansupplementyourphysicalbackupswithlogicalbackupsofschemaobjectsmadeusingtheExportutility.TheutilitywritesdatafromanOracledatabasetobinaryoperatingsystemfiles.YoucanlateruseImporttorestorethisdataintoadatabase.
Thissectioncontainsthefollowingtopics:
∙ConsistentandInconsistentBackups
∙WholeDatabaseandPartialDatabaseBackups
∙RMANandUser-ManagedBackups
SeeAlso:
"WhentoUseImport/ExportUtilitiesRecovery"forinformationonlogicalbackups
ConsistentandInconsistentBackups
Aconsistentbackupisoneinwhichthefilesbeingbackedupcontainallchangesuptothesamesystemchangenumber(SCN).Thismeansthatthefilesinthebackupcontainallthedatatakenfromasamepointintime.Unlikeaninconsistentbackup,aconsistentwholedatabasebackupdoesnotrequirerecoveryafteritisrestored.
Aninconsistentbackupisabackupofoneormoredatabasefilesthatyoumakewhilethedatabaseisopenorafterthedatabasehasshutdownabnormally.
OverviewofConsistentBackups
Aconsistentbackupofadatabaseorpartofadatabaseisabackupinwhichallread/writedatafilesandcontrolfilesarecheckpointedwiththesameSCN.
TheonlywaytomakeaconsistentwholedatabasebackupistoshutdownthedatabasewiththeNORMAL,IMMEDIATE,orTRANSACTIONALoptionsandmakethebackupwhilethedatabaseisclosed.Ifadatabaseisnotshutdowncleanly,forexample,aninstancefailsoryouissueaSHUTDOWNABORTstatement,thenthedatabase'sdatafilesarealwaysinconsistent—unlessthedatabaseisaread-onlydatabase.
OraclemakesthecontrolfilesanddatafilesconsistenttothesameSCNduringadatabasecheckpoint.TheonlytablespacesinaconsistentbackupthatareallowedtohaveolderSCNsareread-onlyandofflinenormaltablespaces,whicharestillconsistentwiththeotherdatafilesinthebackupbecausenochangeshavebeenmadetothem.
Theimportantpointisthatyoucanopenthedatabaseafterrestoringaconsistentwholedatabasebackupwithoutneedingrecoverybecausethedataisalreadyconsistent:
noactionisrequiredtomakethedataintherestoreddatafilescorrect.Hence,youcanrestoreayear-oldconsistentbackupofyourdatabasewithoutperformingmediarecoveryandwithoutOracleperforminginstancerecovery.Ofcourse,whenyourestoreaconsistentwholedatabasebackupwithoutapplyingredo,youlosealltransactionsthatweremadesincethebackupwastaken.
AconsistentwholedatabasebackupistheonlyvalidbackupoptionfordatabasesoperatinginNOARCHIVELOGmode,becauseotherwiserecoveryisnecessaryforconsistency.InNOARCHIVELOGmode,Oracledoesnotarchivetheredologs,andsotherequiredredologsmightnotexistondisk.AconsistentwholebackupisalsoavalidbackupoptionfordatabasesoperatinginARCHIVELOGmode.Whenthistypeofbackupisrestoredandarchivedlogsareavailable,youhavetheoptionofeitheropeningthedatabaseimmediatelyandlosingtransactionsthatweremadesincethebackupwastaken,orapplyingthearchivedlogstorecoverthosetransactions.
OverviewofInconsistentBackups
AninconsistentbackupisabackupinwhichthefilesbeingbackedupdonotcontainallthechangesmadeatalltheSCNs.Inotherwords,somechangesaremissing.Thismeansthatthefilesinthebackupcontaindatatakenfromdifferentpointsintime.Thiscanoccurbecausethedatafilesarebeingmodifiedasbackupsarebeingtaken.Oraclerecoverymakesinconsistentbackupsconsistentbyreadingallarchivedandonlineredologs,startingwiththeearliestSCNinanyofthedatafileheaders,andapplyingthechangesfromthelogsbackintothedatafiles.
Ifthedatabasemustbeupandrunning24hoursaday,sevendaysaweek,thenyouhavenochoicebuttoperforminconsistentbackupsofthewholedatabase.Abackupofonlinedatafilesiscalledanonlinebackup.ThisrequiresthatyourunyourdatabaseinARCHIVELOGmode.
IfyourunthedatabaseinARCHIVELOGmode,thenyoudonothavetobackupthewholedatabaseatonetime.Forexample,ifyourdatabasecontainsseventablespaces,andifyoubackupthecontrolfileaswellasadifferenttablespaceeachnight,theninaweekyouwillbackupalltablespacesinthedatabaseaswellasthecontrolfile.Youcanconsiderthisstaggeredbackupasawholedatabasebackup.However,ifsuchastaggeredbackupmustberestored,thenyouneedtorecoverusingallarchivedredologsthatwerecreatedsincetheearliestbackupwastaken.
Caution:
Oraclestronglyrecommendsthatyoudonotmakeinconsistent,closeddatabasebackupsinNOARCHIVELOGmode.Ifsuchabackupisusedtorestorethedatabase,thendatacorruptionmightresult.
SeeAlso:
OracleDatabaseBackupandRecoveryAdvancedUser'sGuide
ArchivingUnarchivedRedoLogFiles
Afteranonlinebackuporinconsistentclosedbackup,alwaysensurethatyouhavetheredonecessarytorecoverthebackupbyarchivingtheunarchivedredologs.
BackingUptheArchivedLogsandtheControlFile
Afteropenorinconsistentclosedbackups,Oraclerecommendsbackingupallarchivedlogsproducedduringthebackup,andthenbackingupthecontrolfileafterthebackupcompletes.Ifyoudonothaveallarchivedredologsproducedduringthebackup,thenyoucannotrecoverthebackupbecauseyoudonothavealltheredorecordsnecessarytomakeitconsistent.
WholeDatabaseandPartialDatabaseBackups
Thissectioncontainsthefollowingtopics:
∙WholeDatabaseBackups
∙TablespaceBackups
∙DatafileBackups
∙ControlFileBackups
∙ArchivedRedoLogBackups
SeeAlso:
OracleDatabaseUtilitiesforinformationaboutlogicalbackups
WholeDatabaseBackups
Awholedatabasebackupisabackupofeverydatafileinthedatabase,plusthecontrolfile.Wholedatabasebackupsarethemostcommontypeofbackup.
WholedatabasebackupscanbetakenineitherARCHIVELOGorNOARCHIVELOGmode.Beforeperformingwholedatabasebackups,however,beawareoftheimplicationsofbackingupinARCHIVELOGandNOARCHIVELOGmodes.
Figure15-1illustratesthevalidconfigurationoptionsgiventhetypeofbackupthatisperformed.
Figure15-1WholeDatabaseBackupOptions
Descriptionof"Figure15-1WholeDatabaseBackupOptions"
Awholedatabasebackupiseitheraconsistentbackuporaninconsistentbackup.Whetherabackupisconsistentdetermineswhetheryouneedtoapplyredologsafterrestoringthebackup.
TablespaceBackups
Atablespacebackupisabackupofthedatafilesthatconstitutethetablespace.Forexample,iftablespaceuserscontainsdatafiles2,3,and4,thenabackupoftablespaceusersbacksupthesethreedatafiles.
Tablespacebackups,whetheronlineoroffline,arevalidonlyifthedatabaseisoperatinginARCHIVELOGmode.Thereasonisthatredoisrequiredtomaketherestoredtablespaceconsistentwiththeothertablespacesinthedatabase.
DatafileBackups
Adatafilebackupisabackupofasingledatafile.Datafilebackups,whicharenotascommonastablespacebackups,arevalidinARCHIVELOGdatabases.TheonlytimeadatafilebackupisvalidforadatabaseinNOARCHIVELOGmodeisif:
∙Everydatafileinatablespaceisbackedup.Youcannotrestorethedatabaseunlessalldatafilesarebackedup.
∙Thedatafilesarereadonlyoroffline-normal.
SeeAlso:
OracleDatabaseBackupandRecoveryReference
RMANandUser-ManagedBackups
Therearetwotypesofbackups:
imagecopiesandbackupsets.Animagecopyisanexactduplicateofadatafile,controlfile,orarchivedlog.Youcancreateimagecopiesofphysicalfileswithoperatingsystemutilitie
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 15Backup and Recovery 15 Backup