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1、ORACLE回滾段基本概念Thistopicisdividedintothefollowingsections:*roleofrollbacksegment*typeofrollbacksegment*thenumber,size,andstorageparametersoftherollbacksegment*rollbacksectionmaintenanceandquery*commonerrorsandsolutionsforrollbacksegments1.roleofrollbacksegmen
2、tArollbacksegmentforthedatabaseismodified,thepreservationoforiginaldata,sothatlatercanuseROLLBACKtoreturntotheprerevisiondata;inaddition,therollbacksegmentcanprovidereadconsistencyforallprocessesinthedatabase?Therefore,therollbacksettingisreasonableornotdir
3、ectlyaffectstheperformanceofthedatabaseinOLTPapplicationupdateintensive,evenmoreso.2.typeofrollbacksectionTherollbacksegmentcanbedividedintothesystemrollbacksegmentandthenonsystemrollbacksegment,wherethenonsystemrollbacksegmentisdividedintothePUBLICrollback
4、segmentandthePRIVATErollbacksegmentSystemforprocessingrollbacksegmentrelatedCATALOGthings(likemostDDL),whichislocatedintheSYSTEMtablespace,asonlytheSYSTEMtablespacecankeepavailable,sodon，ttakeonotherSYSTEMrollbacksegmenttablespace?***therollbacksectionofthe
5、1:systemshouldbeplacedintheSYSTEMtablespace,andtheONLINEstateshouldalwaysbemaintainedThePUBLICrollbacksegmentisavailableforallinstancesofthedatabase(INSTANCE)unlessitisexplicitlysettoOFFLINE?PRIVATEreferstoarollbackdatabaseinstanceisprivate,inordertousetheP
6、RIVATEhuigunduan,acaseshallbeindicatedallthePRIVATEyouwanttousearollbacksegmentinitsINITsid.ORAROLLBACK_SEGMENTS,orROLLBACKSEGMENTXXXbyusingALTERONLINEtomakearollbacksegment?****recommends1:inasingleinstancesystemandrecommendsthatallrollbacksegmentsbesettoP
7、UBLIC?*****recommends2:inamultiinstancesystem(suchasOPS),whichsuggeststhateachinstance'sPRIVATErollbacksegmentbeplacedonafasteraccesslocaldevice1.thenumber,size,andstorageparametersoftherollbacksegmentCalculatethenumberandsizeoftherollbacksegmentaccuratelyi
8、nvolvesmanyaspects:theapplicationtype(OLTP/OLAP/BATCH),thenumberofthingsatthesametime,thetypeofDMLstatement,eachtransactionamountofdataandsoon.Accuratecalculation,becauseofthelimitedspace,nottomentionh
