1、DCopyright 2004, Oracle. All rights reserved.Oracle Architectural ComponentsD-2Copyright 2004, Oracle. All rights reserved.ObjectivesAfter completing this appendix, you should be able to do the following:Describe the Oracle server architecture and its main componentsList the structures involved in c

2、onnecting a user to an Oracle instanceList the stages in processing: Queries DML statements CommitsD-3Copyright 2004, Oracle. All rights reserved.Oracle Database Architecture: OverviewThe Oracle database consists of two main components:The database or the physical structuresThe instance or the memor

3、y structuresD-4Copyright 2004, Oracle. All rights reserved.Database Physical Architecture Data filesOnline redo log filesPassword fileParameter fileControl filesArchive log filesD-5Copyright 2004, Oracle. All rights reserved.Control FilesContains physical database structure informationMultiplexed to

4、 protect against lossRead at mount stageControl filesD-6Copyright 2004, Oracle. All rights reserved.Redo Log FilesRecord changes to the databaseMultiplexed to protect against lossRedo log bufferLogWriterLGWRGroup 1Group 2Group 3D-7Copyright 2004, Oracle. All rights reserved.Tablespaces and Data File

5、sTablespaces consist of one or more data files.Data files belong to only one tablespace.USERS tablespaceData file 1Data file 2D-8Copyright 2004, Oracle. All rights reserved.Segments, Extents, and BlocksSegments exist within a tablespace.Segments consist of a collection of extents.Extents are a colle

6、ction of data blocks.Data blocks are mapped to OS blocks.SegmentExtentsData blocksOS blocksD-9Copyright 2004, Oracle. All rights reserved.Oracle Instance ManagementSystemMonitorSMONDatabaseWriterDBW0LogWriterLGWRProcessMonitorPMONArchiverARC0SGAJava poolShared poolLarge poolStreams poolDatabasebuffe

7、r cacheRedo log bufferCheckpointCKPTD-10Copyright 2004, Oracle. All rights reserved.Oracle Memory StructuresJava poolDatabasebuffer cacheRedo log bufferShared poolLarge poolSGAStreams poolServerprocess1PGAServerprocess2PGABack-groundprocessPGAD-11Copyright 2004, Oracle. All rights reserved.Oracle Me

8、mory Structures (continued) Full Notes PageD-12Copyright 2004, Oracle. All rights reserved.Oracle ProcessesSystemmonitorSMONDatabasewriterDBW0CheckpointCKPTLogwriterLGWRProcessmonitorPMONArchiverARC0ServerprocessServerprocessServerprocessServerprocessSystem Global AreaSGABackground processesD-13Copy

9、right 2004, Oracle. All rights reserved.Other Key Physical StructuresArchived log filesParameterfilePasswordfileDatabaseD-14Copyright 2004, Oracle. All rights reserved.Processing a SQL StatementConnect to an instance using: The user process The server processThe Oracle server components that are use

10、d depend on the type of SQL statement: Queries return rows DML statements log changes Commit ensures transaction recoverySome Oracle server components do not participate in SQL statement processing.D-15Copyright 2004, Oracle. All rights reserved.Connecting to an InstanceUserServerServerUserClientUse

11、rServerOracle serverServerApplication serverBrowser D-16Copyright 2004, Oracle. All rights reserved.D-17Copyright 2004, Oracle. All rights reserved.Processing a QueryParse: Search for identical statement Check syntax, object names, and privileges Lock objects used during parse Create and store execu

12、tion planExecute: Identify rows selectedFetch: Return rows to user processD-18Copyright 2004, Oracle. All rights reserved.The Shared PoolThe library cache contains the SQL statement text, parsed code, and execution plan.The data dictionary cache contains table, column, and other object definitions a

13、nd privileges.The shared pool is sized by SHARED_POOL_SIZE. Data dictionarycacheLibrarycacheShared poolD-19Copyright 2004, Oracle. All rights reserved.D-20Copyright 2004, Oracle. All rights reserved.Database Buffer CacheStores the most recently used blocksSize of a buffer based on DB_BLOCK_SIZENumbe

14、r of buffers defined by DB_BLOCK_BUFFERS Database buffercacheD-21Copyright 2004, Oracle. All rights reserved.Program Global Area (PGA)Not sharedWritable only by the server processContains: Sort area Session information Cursor state Stack spaceServerprocessPGAD-22Copyright 2004, Oracle. All rights re

15、served.Processing a DML StatementUPDATE employees .SGARedo logbufferDatabase buffercacheShared poolUserprocessServerprocessDatabaseData files Control filesRedolog files11234D-23Copyright 2004, Oracle. All rights reserved.D-24Copyright 2004, Oracle. All rights reserved.Redo Log BufferHas its size def

16、ined by LOG_BUFFERRecords changes made through the instanceIs used sequentiallyIs a circular bufferDatabase buffercache D-25Copyright 2004, Oracle. All rights reserved. Rollback SegmentDML statementOld imageNew imageRollback segmentTableD-26Copyright 2004, Oracle. All rights reserved.COMMIT Processi

17、ng134InstanceSGARedo logbufferDatabase buffercacheShared pool LGWR2UserprocessServerprocessDatabaseData files Control filesRedolog filesD-27Copyright 2004, Oracle. All rights reserved.D-28Copyright 2004, Oracle. All rights reserved.SummaryIn this appendix, you should have learned how to:Identify database files: data files, control files, and online redo logsDescribe SGA memory structures: