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Oracle architecture ppt

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Oracle DB Archutecture

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Oracle architecture ppt

  1. 1. Copyright © 2007, Oracle. All rights reserved. Exploring the Oracle Database Architecture
  2. 2. Copyright © 2007, Oracle. All rights reserved.1 - 2 Objectives After completing this lesson, you should be able to: • List the major architectural components of Oracle Database • Explain the memory structures • Describe the background processes • Correlate the logical and physical storage structures
  3. 3. Copyright © 2007, Oracle. All rights reserved.1 - 3 Oracle Database The Oracle relational database management system (RDBMS) provides an open, comprehensive, integrated approach to information management
  4. 4. Copyright © 2007, Oracle. All rights reserved.1 - 4 Connecting to a Server Client Middle tier Server Multitier architecture shown
  5. 5. Copyright © 2007, Oracle. All rights reserved.1 - 6 Database Data files Online redo log files Control files Oracle Database Architecture: Overview Database buffer cache Shared pool Data dictionary cache Library cache PMONSMON Others Server process PGA Archived log files User process Instance RECO ARCn SGA DBWn Redo log buffer LGWRCKPT
  6. 6. Copyright © 2007, Oracle. All rights reserved.1 - 7 Connecting to the Database • Connection: Communication between a user process and an instance • Session: Specific connection of a user to an instance through a user process SQL> Select … Session Connection User User process Server process Session
  7. 7. Copyright © 2007, Oracle. All rights reserved.1 - 8 Interacting with an Oracle Database User Database buffer cache Shared pool Data dictionary cache Library cache PMONSMON Others Instance RECOARCn SGA DBWn Redo log buffer LGWRCKPT User process Server process
  8. 8. Copyright © 2007, Oracle. All rights reserved.1 - 10 Database Oracle Database Server Structures PMONSMON Others Data files Online redo log files Control files Instance RECOARCnDBWn LGWRCKPT Storage structures User process Server process Memory structures Processes Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  9. 9. Copyright © 2007, Oracle. All rights reserved.1 - 11 Oracle Database Memory Structures DB structures Memory - Process - Storage SGA Database buffer cache Redo log buffer Java pool Streams pool Shared pool Large pool PGA PGA PGA Background process Server process 1 Server process 2 Shared SQL area Library cache Data dictionary cache Other I/O buffer Response queue Request queue Free memory
  10. 10. Copyright © 2007, Oracle. All rights reserved.1 - 13 Database Buffer Cache • Is part of the SGA • Holds copies of data blocks that are read from data files • Is shared by all concurrent users PMONSMON Others Instance RECOARCnDBWn LGWRCKPT Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  11. 11. Copyright © 2007, Oracle. All rights reserved.1 - 14 Redo Log Buffer • Is a circular buffer in the SGA • Holds information about changes made to the database • Contains redo entries that have the information to redo changes made by operations such as DML and DDL PMONSMON Others Instance RECOARCnDBWn LGWRCKPT Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  12. 12. Copyright © 2007, Oracle. All rights reserved.1 - 15 Shared Pool • Is a portion of the SGA • Contains: – Library cache — Shared SQL area – Data dictionary cache – Control structures PMONSMON Others Instance RECOARCnDBWn LGWRCKPT Shared SQL area Library cache Data dictionary cache Other Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  13. 13. Copyright © 2007, Oracle. All rights reserved.1 - 17 Allocation and Reuse of Memory in the Shared Pool • Server process checks the shared pool to see if a shared SQL area already exists for an identical statement. • Server process allocates a private SQL area on behalf of the session. Server process Shared pool Shared SQL area Library cache Data dictionary cache Other
  14. 14. Copyright © 2007, Oracle. All rights reserved.1 - 19 Large Pool Provides large memory allocations for: • Session memory for the shared server and the Oracle XA interface • I/O server processes • Oracle Database backup and restore operations Large pool I/O buffer Response queue Request queue Free memory Java pool Large pool Shared pool Database buffer cache Redo log buffer Streams pool
  15. 15. Copyright © 2007, Oracle. All rights reserved.1 - 20 Java Pool and Streams Pool • Java pool memory is used in server memory for all session-specific Java code and data in the JVM. • Streams pool memory is used exclusively by Oracle Streams to: – Store buffered queue messages – Provide memory for Oracle Streams processes Java pool Streams pool
  16. 16. Copyright © 2007, Oracle. All rights reserved.1 - 21 Process Architecture • User process – Is started when a database user or a batch process connects to Oracle Database • Database processes – Server process: Connects to the Oracle instance and is started when a user establishes a session – Background processes: Are started when an Oracle instance is started DB structures - Memory  Process - Storage PMONSMON Others Instance RECOARCnDBWn LGWRCKPT PGA User process Server process Background processes Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  17. 17. Copyright © 2007, Oracle. All rights reserved.1 - 22 Process Structures Server n processes SGA Oracle background processes PMON SMON OthersRECO ARCnDBWn LGWRCKPT Server ServerServerServer Server Database buffer cache Shared pool Data dictionary cache Library cache SGA Redo log buffer
  18. 18. Copyright © 2007, Oracle. All rights reserved.1 - 24 Database Writer Process (DBWn) Writes modified (dirty) buffers in the database buffer cache to disk: • Asynchronously while performing other processing • Periodically to advance the checkpoint Database buffer cache Database writer process Data files DBWn
  19. 19. Copyright © 2007, Oracle. All rights reserved.1 - 26 LogWriter Process (LGWR) • Writes the redo log buffer to a redo log file on disk • Writes: – When a user process commits a transaction – When the redo log buffer is one-third full – Before a DBWn process writes modified buffers to disk Redo log buffer LogWriter process Redo log files LGWR
  20. 20. Copyright © 2007, Oracle. All rights reserved.1 - 28 Checkpoint Process (CKPT) • Records checkpoint information in – Control file – Each data file header Checkpoint process Data files Control fileCKPT
  21. 21. Copyright © 2007, Oracle. All rights reserved.1 - 29 System Monitor Process (SMON) • Performs recovery at instance startup • Cleans up unused temporary segments Instance Temporary segment System Monitor process SMON
  22. 22. Copyright © 2007, Oracle. All rights reserved.1 - 30 Process Monitor Process (PMON) • Performs process recovery when a user process fails – Cleans up the database buffer cache – Frees resources that are used by the user process • Monitors sessions for idle session timeout • Dynamically registers database services with listeners Process Monitor process Database buffer cache Failed user process UserPMON
  23. 23. Copyright © 2007, Oracle. All rights reserved.1 - 31 Recoverer Process • Used with the distributed database configuration • Automatically connects to other databases involved in in-doubt distributed transactions • Automatically resolves all in-doubt transactions • Removes any rows that correspond to in-doubt transactions Recoverer process in database A In-doubt transaction in database B RECO
  24. 24. Copyright © 2007, Oracle. All rights reserved.1 - 32 Archiver Processes (ARCn) • Copy redo log files to a designated storage device after a log switch has occurred • Can collect transaction redo data and transmit that data to standby destinations Archiver process Archive destinationCopies of redo log files ARCn
  25. 25. Copyright © 2007, Oracle. All rights reserved.1 - 33 Other Processes • MMON: Performs manageability-related background tasks • MMNL: Performs frequent and lightweight manageability-related tasks • MMAN: Performs automatic memory management tasks • CJQ0: Runs user jobs used in batch processing • QMNx: Monitors the Streams Advanced Queuing message queues
  26. 26. Copyright © 2007, Oracle. All rights reserved.1 - 35 Server Process and Database Buffer Cache Buffers: • Pinned • Clean • Free or unused • Dirty Database writer process Database buffer cache SGA Data files DBWn Server process
  27. 27. Copyright © 2007, Oracle. All rights reserved.1 - 36 Database Storage Architecture Online redo log files Password file Parameter file Archived redo log files Control files Data files Alert log and trace files Backup files DB structures - Memory - Process  Storage
  28. 28. Copyright © 2007, Oracle. All rights reserved.1 - 38 Logical and Physical Database Structures Database Logical Physical Tablespace Data file OS block Segment Extent Oracle data block Schema
  29. 29. Copyright © 2007, Oracle. All rights reserved.1 - 40 Tablespaces and Data Files • Tablespaces consist of one or more data files. • Data files belong to only one tablespace. USERS tablespace Data file 1 Data file 2
  30. 30. Copyright © 2007, Oracle. All rights reserved.1 - 41 SYSTEM and SYSAUX Tablespaces • The SYSTEM and SYSAUX tablespaces are mandatory tablespaces that are created at the time of database creation. They must be online. • The SYSTEM tablespace is used for core functionality (for example, data dictionary tables). • The auxiliary SYSAUX tablespace is used for additional database components (such as the Enterprise Manager Repository).
  31. 31. Copyright © 2007, Oracle. All rights reserved.1 - 42 Segments, Extents, and Blocks • Segments exist in a tablespace. • Segments are collections of extents. • Extents are collections of data blocks. • Data blocks are mapped to disk blocks. Segment Extents Data blocks Disk blocks
  32. 32. Copyright © 2007, Oracle. All rights reserved.1 - 43 Database Architecture: Summary of Structural Components • Memory structures: – System Global Area (SGA): Database buffer cache, redo buffer, and various pools – Program Global Area (PGA) • Process structures: – User process and server process – Background processes: SMON, PMON, DBWn, CKPT, LGWR, ARCn, and so on • Storage structures: – Logical: Database, schema, tablespace, segment, extent, and Oracle block – Physical: Data files, control files, and redo log files
  33. 33. Copyright © 2007, Oracle. All rights reserved.1 - 44 Summary In this lesson, you should have learned how to: • List the major architectural components of Oracle Database • Explain the memory structures • Describe the background processes • Correlate the logical and physical storage structures
  34. 34. Copyright © 2007, Oracle. All rights reserved.1 - 45 Practice 1: Overview This is a paper practice with questions about: • Database architecture • Memory • Processes • File structures

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