Less01 architecture

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Less01 architecture

  1. 1. 1Exploring the Oracle Database Architecture Copyright © 2009, Oracle. All rights reserved.
  2. 2. ObjectivesAfter 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 • Describe ASM storage components1-2 Copyright © 2009, Oracle. All rights reserved.
  3. 3. Oracle DatabaseThe Oracle relational database management system (RDBMS)provides an open, comprehensive, integrated approach toinformation management1-3 Copyright © 2009, Oracle. All rights reserved.
  4. 4. Connecting to a Server Client Middle tier Server Multitier architecture shown1-4 Copyright © 2009, Oracle. All rights reserved.
  5. 5. Oracle Database Server Architecture: Overview Instance PGA Server process Memory Structures (System Global Area) Server Process Structures User process Database (Storage Structures) Client1-6 Copyright © 2009, Oracle. All rights reserved.
  6. 6. Instance: Database Configurations Nonclustered System Clustered System I1 I1 I2 I3 I2 D1 D2 Local D Storage Shared Storage1-7 Copyright © 2009, Oracle. All rights reserved.
  7. 7. Connecting to the Database Instance • Connection: Communication between a user process and an instance • Session: Specific connection of a user to an instance through a user process User Server SQL> Select … process process User Session Connection Session1-8 Copyright © 2009, Oracle. All rights reserved.
  8. 8. Oracle Database Memory Structures Program Global Area (PGA) PGA Stack User Stack User Space Global Space Global Area Area Server Server process 1 process 2 KEEP Database Redo log buffer pool Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache System Global Area (SGA)1-9 Copyright © 2009, Oracle. All rights reserved.
  9. 9. Shared Pool • Is a portion of the SGA • Contains: – Library cache Shared Data dictionary SQL area cache — Shared SQL area – Data dictionary cache Fixed Area – Control structures Library Other cache KEEP Database buffer pool Redo log Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache System Global Area (SGA)1 - 11 Copyright © 2009, Oracle. All rights reserved.
  10. 10. 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 KEEP Database Redo log buffer pool Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache System Global Area (SGA)1 - 13 Copyright © 2009, Oracle. All rights reserved.
  11. 11. 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 KEEP Database Redo log buffer pool Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache System Global Area (SGA)1 - 14 Copyright © 2009, Oracle. All rights reserved.
  12. 12. 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 KEEP Database Redo log buffer pool Shared pool buffer buffer Free Parallel cache I/O buffer RECYCLEmemory Query buffer pool Response Request Advanced Streams queuebuffer queue nK Queuing Large pool Java pool pool cache Large pool System Global Area (SGA)1 - 15 Copyright © 2009, Oracle. All rights reserved.
  13. 13. Java Pool and Streams Pool • Java pool memory is used to store 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 KEEP Database Redo log buffer pool Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache Java pool Streams System Global Area (SGA) pool1 - 16 Copyright © 2009, Oracle. All rights reserved.
  14. 14. Program Global Area (PGA) PGA Cursor Sort Hash Area Area State Stack User Create Bitmap Area Space Global User Session Area Data Bitmap Merge Area Server process 1 SQL Working Areas KEEP Database Redo log buffer pool Shared pool buffer buffer cache RECYCLE buffer pool Streams nK buffer Large pool Java pool pool cache System Global Area (SGA)1 - 17 Copyright © 2009, Oracle. All rights reserved.
  15. 15. Quiz Memory region that contains data and control information for a server or background process is called: 1. Shared Pool 2. PGA 3. Buffer Cache 4. User session data1 - 18 Copyright © 2009, Oracle. All rights reserved.
  16. 16. Quiz What is read into the Database Buffer Cache from the data files? 1. Rows 2. Changes 3. Blocks 4. SQL1 - 19 Copyright © 2009, Oracle. All rights reserved.
  17. 17. Process Architecture • User process – Is the application or tool that connects to the 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 • Daemon / Application processes – Networking listeners – Grid infrastructure daemons1 - 20 Copyright © 2009, Oracle. All rights reserved.
  18. 18. Process Structures Instances (ASM and Database separate) System Global Area (SGA) PGA Server Background processes process Required: DBWn CKPT LGWR SMON PMON RECO Optional: ARCn ASMB RBAL Others Listener Grid Infrastructure Processes (ASM and Oracle Restart) User ohas ocssd diskmon process orarootagent oraagent cssdagent1 - 21 Copyright © 2009, Oracle. All rights reserved.
  19. 19. Database Writer Process (DBWn) Writes modified (dirty) buffers in the database buffer cache to disk: • Asynchronously while performing other processing • To advance the checkpoint DBWn Database buffer Database writer Data files cache process1 - 23 Copyright © 2009, Oracle. All rights reserved.
  20. 20. Log Writer 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 – Every 3 seconds LGWR Redo log buffer Log Writer process Redo log files1 - 25 Copyright © 2009, Oracle. All rights reserved.
  21. 21. Checkpoint Process (CKPT) • Records checkpoint information in – Control file – Each data file header CKPT Control file Checkpoint process Data files1 - 27 Copyright © 2009, Oracle. All rights reserved.
  22. 22. System Monitor Process (SMON) • Performs recovery at instance startup • Cleans up unused temporary segments Instance SMON System Monitor process Temporary segment1 - 28 Copyright © 2009, Oracle. All rights reserved.
  23. 23. 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 Server process PMON User tnslsnr Database buffer Failed user Process Monitor cache process process1 - 29 Copyright © 2009, Oracle. All rights reserved.
  24. 24. 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 RECO Recoverer process In-doubt transaction in database A in database B1 - 30 Copyright © 2009, Oracle. All rights reserved.
  25. 25. 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 ARCn Archiver process Copies of redo log Archive destination files1 - 31 Copyright © 2009, Oracle. All rights reserved.
  26. 26. Process Startup Sequence • Oracle Grid Infrastructure is started by the OS init daemon. Operating System Grid Infrastructure Grid Infrastructure Init Daemon Wrapper Script Daemons and Processes init ohasd.bin init.ohasd oraagent.bin ASM Instance (root) Listener orarootagent.bin DB Instance diskmon.bin User Defined cssdagent ocssd.bin Applications • Oracle Grid Infrastructure installation modifies the /etc/inittab file to ensure startup every time machine is started in corresponding run level. # cat /etc/inittab .. h1:35:respawn:/etc/init.d/init.ohasd run >/dev/null 2>&1 </dev/null1 - 32 Copyright © 2009, Oracle. All rights reserved.
  27. 27. Database Storage Architecture Control files Data files Online redo log files Parameter file Backup files Archived redo log files Password file Alert log and trace files1 - 33 Copyright © 2009, Oracle. All rights reserved.
  28. 28. Logical and Physical Database Structures Logical Physical Database Tablespace Data file Segment Storage System • SAN • NFS Extent • NAS • ASM • Exadata • RAW Oracle data block • File System1 - 35 Copyright © 2009, Oracle. All rights reserved.
  29. 29. 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 Disk blocks blocks (File System Storage)1 - 37 Copyright © 2009, Oracle. All rights reserved.
  30. 30. Tablespaces and Data Files Tablespace 1 Tablespace 2 (Bigfile) Datafile 1 Datafile 2 Datafile 3 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb Only 1 datafile 8Kb 8Kb 8Kb 8Kb 8Kb allowed 8Kb 8Kb 8Kb 8Kb 8Kb <= 128 TB Extent Extent 64KB 96KB Segment 160KB1 - 38 Copyright © 2009, Oracle. All rights reserved.
  31. 31. 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). • The SYSTEM and SYSAUX tablespaces are not recommended to be used to store applications data.1 - 39 Copyright © 2009, Oracle. All rights reserved.
  32. 32. Automatic Storage Management • Is a portable and high-performance cluster file system • Manages Oracle database files Oracle Application Database • Manages application files with ASM Cluster File System (ACFS) • Spreads data across disks ASM Cluster File to balance load System ASM Files for Oracle • Mirrors data in case of failures Database ASM Dynamic • Solves storage-management Volume Manager challenges Automatic Storage Management Operating system1 - 40 Copyright © 2009, Oracle. All rights reserved.
  33. 33. ASM Storage Components ASM Oracle ASM Database ASM file disk group datafile ASM extent File system or ASM allocation Raw device ASM disk unit1 - 41 Copyright © 2009, Oracle. All rights reserved.
  34. 34. Interacting with an Oracle Database: Memory, Processes and Storage Instance Database KEEP Redo log buffer Shared buffer PGA buffer pool cache RECYCLE Server buffer process Java Streams nK buffer Large pool pool pool cache Listener DBWn CKPT LGWR SMON PMON RECO ARCn Others User process User1 - 42 Copyright © 2009, Oracle. All rights reserved.
  35. 35. Quiz The Process Monitor process (PMON): 1. Performs recovery at instance startup 2. Performs process recovery when a user process fails 3. Automatically resolves all in-doubt transactions 4. Writes the redo log buffer to a redo log file1 - 44 Copyright © 2009, Oracle. All rights reserved.
  36. 36. Quiz ASM Files are accessed by which types of instances? 1. RDBMS Instances only 2. ASM Instances only 3. Both RDBMS and ASM Instances1 - 45 Copyright © 2009, Oracle. All rights reserved.
  37. 37. 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 • Describe the ASM storage components1 - 46 Copyright © 2009, Oracle. All rights reserved.
  38. 38. Practice 1: Overview This is a paper practice with questions about: • Database architecture • Memory • Processes • File structures1 - 47 Copyright © 2009, Oracle. All rights reserved.

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