Oracle英文版培训课件之Implement Streams：les07

CaptureProcess:ConceptsObjectivesAftercompletingthislesson,youshouldbeabletodothefollowing:DescribethefunctionofthecaptureprocessListthetypesofchangesthatarecapturedDescribethecapture-processarchitectureDiscussStreamstagsandthewaystheyareusedduringcaptureCaptureStreamseventscanbeenqueuedintwoways.Implicitly:Log-basedcaptureofDMLandDDLExplicitly:DirectenqueueofusermessagesEventsareenqueuedinastagingarea.SGAStreams

poolEnqueueCaptureRulesImplicitEventCaptureLog-basedchangecaptureprovideslow-overhead,

low-latencychangecapture:Changestothedatabasearewrittentotheonlineredolog.OracleStreamsextractschangesfromtheonlinelog(hotmining)orarchivedlogs.Changesareformattedasalogicalchangerecord(LCR),arepresentationofthechange.LCRsareplacedintheStreamsstagingareaforfurtherprocessing.CaptureProcess:ComponentsThecaptureprocessusesthefollowingparallelexecutionserverstocapturechangesconcurrently:Onereaderservertoreadchangesfromthe

redologanddividetheredologintoregionsAnumberofpreparerserverstoscantheredologregionsandprefilterthechangeeventsOnebuilderservertomergeredorecordsfromthepreparerserversP003buildP000readP001prepparallelism=2P002prepC001IdentifyingChangestoCaptureAcaptureprocessusesrulestodeterminewhichchangesarecaptured.Thecaptureprocesscompletesthefollowingsteps:FindschangesintheredologsPrefilterschangesattheobjectandschemalevelFormatsthechangesasLCRsPerformsLCRfilteringanddiscardsselectedchangesEnqueuestheremainingLCRsRowLCRsArowLCRdescribesaDMLchangetothedatainasingleroworaLOBcolumninarow:AsingledatachangemayyieldmultipleLCRs.EachrowLCRcontains:SourcedatabasenameSCNwhenthechangewaswrittentotheredologDMLstatementtypeSchemaandtablenameTrackingtagTransactionIDBeforevalues(asappropriate)Aftervalues(asappropriate)DDLLCRsADDLLCRdescribesadatadefinitionlanguagechange.EachDDLLCRcontains:SourcedatabasenameDDLstatementtypeObjectowner,name,andtypeTextoftheDDLstatementCurrentschemafortheDDLstatementBasetableownerandnameTrackingtagandtransactionIDSCNwhenthechangewaswrittentotheredologDataTypesCapturedAcaptureprocess:CaptureschangesmadetothecolumnsofallOracledatatypesexcept:BFILEROWIDUser-definedtypes(includingobjecttypes,REFs,VARRAYs,andnestedtables)Oracle-suppliedobjecttypesTransparentDataEncryptionencryptedcolumnsRaisesanerrorifchangesaremadetothecolumnsofunsupportedtypesTypesofDMLChangesCapturedAcaptureprocesssupportsthefollowingDMLchanges:INSERT,UPDATE,andMERGEDELETEPiecewiseupdatestoLOBsAcaptureprocessdoesnotcapturechangesmadeto:TemporaryorobjecttablesSYSandSYSTEMobjectsCaptureofunsupporteddatatypes

causesthecaptureprocessto

raiseanerror.TypesofDDLCapturedAcaptureprocesssupportsDDLchangestothefollowingtypesofobjects:TablesIndexesViewsSequencesSynonymsPL/SQLpackages,procedures,andfunctionsTriggersChangestousersorrolesGRANTorREVOKEonusersorrolesCommandsNotCapturedALTERSESSIONALTERSYSTEMCALLorEXECUTEforPL/SQLproceduresEXPLAINPLANLOCKTABLESETROLENOLOGGINGorUNRECOVERABLEoperationsFLASHBACKDATABASEDDLThatIsNotSupportedCREATECONTROLFILECREATEorALTERDATABASECREATE,ALTER,orDROPMATERIALIZEDVIEWLOGCREATE,ALTER,orDROPMATERIALIZEDVIEW

CREATE,ALTER,orDROPSUMMARYCREATESCHEMACREATEPFILECREATESPFILERENAME(useALTERTABLEinstead)ViewingObjectsNotSupportedByCaptureSELECT*FROMDBA_STREAMS_UNSUPPORTEDWHEREownerIN('OE','PM','SH','IX');OWNERTABLE_NAME-----------------------------------------------------REASONAUTO---------------------------------------------OE CUSTOMERScolumnwithuser-definedtypeNOIXAQ$_ORDERS_QUEUETABLE_SAQqueuetableNOPMTEXTDOCS_NESTEDTABcolumnwithuser-definedtypeNOSHDR$SUP_TEXT_IDX$KunsupportedcolumnexistsYES…LimitingCapturedEventsYoucanuserulestolimitwhatiscaptured:OnlyDMLrulesoronlyDDLrulesNegativerulesSubsetrulesComplexrulesRulesbasedonStreamstagsStreamsTagsEveryredoentryintheredologhasatagassociatedwithit.Youcanusetagstoidentifythesourceofthegeneratedredo.TagsbecomepartoftheLCRsthatarecreatedbyacaptureprocess.tag=>HEXTORAW('APP1');LGWRtag=>NULL;StreamsTagsBydefault,whenauserorapplicationgeneratesredoentries,thetagisNULLforeachredoentry.Redoentriesthataregeneratedbyanapplyprocessuseadefaulttagvalueof“00”(doublezero).Youcanspecifynon-NULLtagsforredoentriesthataregeneratedbyacertainsessionorbyanapplyprocess.AlteringtheValueofStreamsTagsYoucancontrolthevalueofthetagsthataregeneratedintheredologinthefollowingways:UsetheDBMS_STREAMS.SET_TAGproceduretospecifythevalueoftheredotagsthataregeneratedinthecurrentsession.UsetheSET_TAGmemberprocedureforanexi