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OracleArchitecturalComponentsObjectivesAftercompletingthislesson,youshouldbeabletodothefollowing:OutlinetheOraclearchitectureanditsmaincomponentsListthestructuresinvolvedinconnectingausertoanOracleinstancePasswordfileOverviewofPrimaryComponentsInstanceSGARedoLog

BufferSharedPoolDataDictionary

CacheLibraryCacheDBWRSMONPMONCKPTLGWROthersUser

processServer

processPGAControlfilesDatafilesDatabaseDatabase

BufferCacheRedoLogfilesJavaPoolLargePoolParameterfileArchivedLogfilesOracleServerAnOracleserver:Isadatabasemanagementsystemthatprovidesanopen,comprehensive,integratedapproachtoinformationmanagementConsistsofanOracleinstanceandanOracledatabaseOracleserverOracleInstanceAnOracleinstance:IsameanstoaccessanOracledatabaseAlwaysopensoneandonlyonedatabaseConsistsofmemoryandbackgroundprocessstructuresBackgroundprocessstructuresMemorystructuresInstanceSGARedoLog

BufferSharedPoolDataDictionary

CacheLibraryCacheDBWRSMONPMONCKPTLGWROthersDatabase

BufferCacheJavaPoolLargePoolEstablishingaConnection

andCreatingaSessionConnectingtoanOracleinstance: Establishingauserconnection CreatingasessionSessioncreatedDatabaseuserUser

processServer

processConnectionestablishedOracleserverOracleDatabaseAnOracledatabase:IsacollectionofdatathatistreatedasaunitConsistsofthreefiletypesPasswordfileParameterfileArchivedLogfilesControlfilesDatafilesRedoLogfilesOracleDatabasePhysicalStructureThephysicalstructureincludesthreetypesoffiles:ControlfilesDatafilesOnlineredologfilesControlfilesDatafiles(includesDataDictionary)HeaderOnlineRedoLogfilesMemoryStructureOracle’smemorystructureconsistsoftwomemoryareasknownas:SystemGlobalArea(SGA):Allocatedatinstancestartup,andisafundamentalcomponentofanOracleinstanceProgramGlobalArea(PGA):AllocatedwhentheserverprocessisstartedSystemGlobalAreaTheSGAconsistsofseveralmemorystructures:SharedPoolDatabaseBufferCacheRedoLogBufferOtherstructures(forexample,lockandlatchmanagement,statisticaldata)TherearetwoadditionalmemorystructuresthatcanbeconfiguredwithintheSGA:LargePoolJavaPoolSystemGlobalAreaIsdynamicSizedbytheSGA_MAX_SIZEparameterAllocatedandtrackedingranulesbySGAcomponentsContiguousvirtualmemoryallocationGranulesizebasedontotalestimatedSGA_MAX_SIZESharedPoolUsedtostore:MostrecentlyexecutedSQLstatementsMostrecentlyuseddatadefinitionsItconsistsoftwokeyperformance-relatedmemorystructures:LibraryCacheDataDictionaryCacheSizedbytheparameter

SHARED_POOL_SIZESharedPoolData

DictionaryCacheLibraryCacheALTERSYSTEMSETSHARED_POOL_SIZE=64M;LibraryCacheStoresinformationaboutthemostrecentlyusedSQLandPL/SQLstatementsEnablesthesharingofcommonlyusedstatementsIsmanagedbyaleastrecentlyused(LRU)algorithmConsistsoftwostructures:SharedSQLareaSharedPL/SQLareaSizedeterminedbytheSharedPoolsizingDataDictionaryCacheAcollectionofthemostrecentlyuseddefinitionsinthedatabaseIncludesinformationaboutdatabasefiles,tables,indexes,columns,users,privileges,andotherdatabaseobjectsDuringtheparsephase,theserverprocesslooksatthedatadictionaryforinformationtoresolveobjectnamesandvalidateaccessCachingdatadictionaryinformationintomemoryimprovesresponsetimeonqueriesandDMLSizedeterminedbytheSharedPoolsizingDatabaseBufferCacheStorescopiesofdatablocksthathavebeenretrievedfromthedatafilesEnablesgreatperformancegainswhenyouobtainandupdatedataManagedthroughanLRUalgorithmDB_BLOCK_SIZEdeterminesprimaryblocksizeDatabaseBuffer

CacheDatabaseBufferCacheConsistsofindependentsubcaches:DB_CACHE_SIZEDB_KEEP_CACHE_SIZEDB_RECYCLE_CACHE_SIZECanbedynamicallyresizedDB_CACHE_ADVICEsettogatherstatisticsforpredictingdifferentcachesizebehaviorStatisticsdisplayedbyV$DB_CACHE_ADVICEALTERSYSTEMSETDB_CACHE_SIZE=96M;RedoLogBufferRecordsallchangesmadetothedatabasedatablocksPrimarypurposeisrecoveryChangesrecordedwithinarecalledredoentriesRedoentriescontaininformationtoreconstructorredochangesSizedefinedbyLOG_BUFFERRedoLog

BufferLargePoolAnoptionalareaofmemoryintheSGARelievestheburdenplacedontheSharedPoolUsedfor:Sessionmemory(UGA)fortheSharedServerI/OserverprocessesBackupandrestoreoperationsorRMANParallelexecutionmessagebuffersPARALLEL_AUTOMATIC_TUNINGsettoTRUEDoesnotuseanLRUlistSizedbyLARGE_POOL_SIZECanbedynamicallyresizedJavaPoolServicesparsingrequirementsforJavacommandsRequiredifinstallingandusingJavaSizedbyJAVA_POOL_SIZEparameterProgramGlobalAreaMemoryreservedforeachuserprocessconnectingtoanOracledatabaseAllocatedwhenaprocessiscreatedDeallocatedwhentheprocessisterminatedUsedbyonlyoneprocessUser

processPGAServer

processProcessStructureOracletakesadvantageofvarioustypesofprocesses:Userprocess:StartedatthetimeadatabaseuserrequestsconnectiontotheOracleserverServerprocess:ConnectstotheOracleinstanceandisstartedwhenauserestablishesasessionBackgroundprocesses:StartedwhenanOracleinstanceisstartedUserProcessAprogramthatrequestsinteractionwiththeOracleserverMustfirstestablishaconnectionDoesnotinteractdirectlywiththeOracleserverDatabaseuserServer

processUser

processConnection

establishedServerProcessAprogramthatdirectlyinteractswiththeOracleserverFulfillscallsgeneratedandreturnsresultsCanbededicatedorsharedserverConnectionestablishedSessioncreatedDatabaseuserUser

processServer

processOracleserverBackgroundProcessesMaintainsandenforcesrelationshipsbetweenphysicalandmemorystructures:Mandatorybackgroundprocesses:DBWn PMON CKPTLGWR SMON Optionalbackgroundprocesses:ARCn LMDn QMNnCJQ0 LMON RECODnnn LMS Snnn LCKn PnnnDatabaseWriter(DBWn)DBWnwriteswhen:CheckpointoccursDirtybuffersreachthresholdTherearenofreebuffersTimeoutoccursRACpingrequestismadeTablespaceOFFLINETablespaceREADONLYTableDROPorTRUNCATETablespaceBEGINBACKUPInstanceSGAControlfilesDatafilesRedoLogfilesDatabaseDBWnDatabaseBuffer

CacheLogWriter(LGWR)LGWRwrites:AtcommitWhenone-thirdfullWhenthereis1MBofredoEverythreesecondsBeforeDBWnwritesInstanceSGAControlfilesDatafilesRedoLogfilesDatabaseRedoLogBufferDBWnLGWRSystemMonitor(SMON)

Responsibilities:InstancerecoveryRollsforwardchangesinonlineredologfilesOpensdatabaseforuseraccessRollsbackuncommittedtransactionsCoalescesfreespaceDeallocatestemporarysegmentsControlfilesDatafilesRedoLogfilesDatabaseInstanceSGASMONProcessMonitor(PMON)Cleansupafterfailedprocessesby:RollingbackthetransactionReleasinglocksReleasingotherresourcesRestartingdeaddispatchersPGAareaInstanceSGAPMONCheckpoint(CKPT)Responsiblefor:SignalingDBWnatcheckpointsUpdatingdatafileheaderswithcheckpointinformationUpdatingcontrolfileswithcheckpointinformationControlfilesDatafilesRedoLogfilesDatabaseInstanceSGADBWnLGWRCKPTArchiver(ARCn)OptionalbackgroundprocessAutomaticallyarchivesonlineredologfileswhenARCHIVELOGmodeissetPreservestherecordofallchangesmadetothedatabaseARCnArchivedredologfilesControlfilesDatafilesRedologfilesLogicalStructureDictateshowthephysicalspaceofadatabaseisusedHierarchyconsistingoftablespaces,segments,extents,andblocksTablespaceDatafileSegmentBlocksExtentSegmentProcessingSQLStatementsConne

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