Exploring the Oracle Database Architecture.ppt
- 1. Copyright © 2009, Oracle. All rights reserved. Exploring the Oracle Database Architecture
- 2. Copyright © 2009, 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 • Describe ASM storage components
- 3. Copyright © 2009, 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. Copyright © 2009, Oracle. All rights reserved. 1 - 4 Connecting to a Server Client Middle tier Server Multitier architecture shown
- 5. Copyright © 2009, Oracle. All rights reserved. 1 - 6 Database (Storage Structures) Oracle Database Server Architecture: Overview Server process PGA User process Instance Memory Structures (System Global Area) Process Structures Client Server
- 6. Copyright © 2009, Oracle. All rights reserved. 1 - 7 Instance: Database Configurations D1 D2 I1 I2 I1 I2 I3 D Clustered System Nonclustered System Local Storage Shared Storage
- 7. Copyright © 2009, Oracle. All rights reserved. 1 - 8 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 SQL> Select … Session Connection User User process Server process Session
- 8. Copyright © 2009, Oracle. All rights reserved. 1 - 9 Oracle Database Memory Structures Server process 1 Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool Stack Space System Global Area (SGA) Program Global Area (PGA) Server process 2 KEEP buffer pool RECYCLE buffer pool nK buffer cache User Global Area Stack Space User Global Area PGA
- 9. Copyright © 2009, Oracle. All rights reserved. 1 - 11 Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool System Global Area (SGA) KEEP buffer pool RECYCLE buffer pool nK buffer cache Shared Pool • Is a portion of the SGA • Contains: – Library cache — Shared SQL area – Data dictionary cache – Control structures Shared SQL area Library cache Data dictionary cache Other Fixed Area
- 10. Copyright © 2009, Oracle. All rights reserved. 1 - 13 Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool System Global Area (SGA) KEEP buffer pool RECYCLE buffer pool nK buffer cache 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
- 11. Copyright © 2009, 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 Shared pool Database buffer cache Streams pool Large pool Java pool System Global Area (SGA) KEEP buffer pool RECYCLE buffer pool nK buffer cache Redo log buffer
- 12. Copyright © 2009, Oracle. All rights reserved. 1 - 15 Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool System Global Area (SGA) KEEP buffer pool RECYCLE buffer pool nK buffer cache 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 Parallel Query Advanced Queuing
- 13. Copyright © 2009, Oracle. All rights reserved. 1 - 16 Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool System Global Area (SGA) KEEP buffer pool RECYCLE buffer pool nK buffer cache 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 Java pool Streams pool
- 14. Copyright © 2009, Oracle. All rights reserved. 1 - 17 Program Global Area (PGA) Server process 1 Stack Space System Global Area (SGA) PGA Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool KEEP buffer pool RECYCLE buffer pool nK buffer cache User Global Area User Session Data Cursor State Sort Area Hash Area Create Bitmap Area SQL Working Areas Bitmap Merge Area
- 15. Copyright © 2009, Oracle. All rights reserved. 1 - 18 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 data
- 16. Copyright © 2009, Oracle. All rights reserved. 1 - 19 Quiz What is read into the Database Buffer Cache from the data files? 1. Rows 2. Changes 3. Blocks 4. SQL
- 17. Copyright © 2009, Oracle. All rights reserved. 1 - 20 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 daemons
- 18. Copyright © 2009, Oracle. All rights reserved. 1 - 21 Process Structures PMON SMON Others Instances (ASM and Database separate) RECO ARCn DBWn LGWR CKPT PGA Background processes System Global Area (SGA) Required: ASMB RBAL Optional: Grid Infrastructure Processes (ASM and Oracle Restart) orarootagent ohas ocssd diskmon oraagent cssdagent User process Server process Listener
- 19. Copyright © 2009, Oracle. All rights reserved. 1 - 23 Database Writer Process (DBWn) Writes modified (dirty) buffers in the database buffer cache to disk: • Asynchronously while performing other processing • To advance the checkpoint Database buffer cache Database writer process Data files DBWn
- 20. Copyright © 2009, Oracle. All rights reserved. 1 - 25 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 Redo log buffer Log Writer process Redo log files LGWR
- 21. Copyright © 2009, Oracle. All rights reserved. 1 - 27 Checkpoint Process (CKPT) • Records checkpoint information in – Control file – Each data file header Checkpoint process Data files Control file CKPT
- 22. Copyright © 2009, Oracle. All rights reserved. 1 - 28 System Monitor Process (SMON) • Performs recovery at instance startup • Cleans up unused temporary segments Instance Temporary segment System Monitor process SMON
- 23. Copyright © 2009, Oracle. All rights reserved. 1 - 29 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 User PMON Server process tnslsnr
- 24. Copyright © 2009, Oracle. All rights reserved. 1 - 30 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
- 25. Copyright © 2009, Oracle. All rights reserved. 1 - 31 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 destination Copies of redo log files ARCn
- 26. Copyright © 2009, Oracle. All rights reserved. 1 - 32 • Oracle Grid Infrastructure is started by the OS init daemon. • Oracle Grid Infrastructure installation modifies the /etc/inittab file to ensure startup every time machine is started in corresponding run level. Process Startup Sequence init.ohasd (root) ohasd.bin oraagent.bin orarootagent.bin diskmon.bin cssdagent ocssd.bin init Grid Infrastructure Wrapper Script Grid Infrastructure Daemons and Processes Operating System Init Daemon # cat /etc/inittab .. h1:35:respawn:/etc/init.d/init.ohasd run >/dev/null 2>&1 </dev/null ASM Instance Listener DB Instance User Defined Applications
- 27. Copyright © 2009, Oracle. All rights reserved. 1 - 33 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
- 28. Copyright © 2009, Oracle. All rights reserved. 1 - 35 Logical and Physical Database Structures Database Logical Physical Tablespace Data file Segment Extent Oracle data block Storage System • SAN • NAS • Exadata • File System • NFS • ASM • RAW
- 29. Copyright © 2009, Oracle. All rights reserved. 1 - 37 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 (File System Storage)
- 30. Copyright © 2009, Oracle. All rights reserved. 1 - 38 Tablespaces and Data Files 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb 8Kb Tablespace 1 Datafile 1 Datafile 2 Extent 64KB Extent 96KB Segment 160KB Tablespace 2 (Bigfile) Datafile 3 Only 1 datafile allowed <= 128 TB
- 31. Copyright © 2009, Oracle. All rights reserved. 1 - 39 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 application's data.
- 32. Copyright © 2009, Oracle. All rights reserved. 1 - 40 Automatic Storage Management • Is a portable and high-performance cluster file system • Manages Oracle database files • Manages application files with ASM Cluster File System (ACFS) • Spreads data across disks to balance load • Mirrors data in case of failures • Solves storage-management challenges ASM Cluster File System ASM Dynamic Volume Manager Application Oracle Database Operating system ASM Files for Oracle Database Automatic Storage Management
- 33. Copyright © 2009, Oracle. All rights reserved. 1 - 41 ASM Storage Components Oracle Database datafile ASM allocation unit ASM disk group ASM disk ASM file ASM extent File system or Raw device ASM
- 34. Copyright © 2009, Oracle. All rights reserved. 1 - 42 Interacting with an Oracle Database: Memory, Processes and Storage User PGA User process Server process Listener PMON SMON Others Instance RECO DBWn LGWR CKPT Shared pool Database buffer cache Redo log buffer Streams pool Large pool Java pool KEEP buffer RECYCLE buffer nK buffer cache ARCn
- 35. Copyright © 2009, Oracle. All rights reserved. 1 - 44 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 file
- 36. Copyright © 2009, Oracle. All rights reserved. 1 - 45 Quiz ASM Files are accessed by which types of instances? 1. RDBMS Instances only 2. ASM Instances only 3. Both RDBMS and ASM Instances
- 37. Copyright © 2009, Oracle. All rights reserved. 1 - 46 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 components
- 38. Copyright © 2009, Oracle. All rights reserved. 1 - 47 Practice 1: Overview This is a paper practice with questions about: • Database architecture • Memory • Processes • File structures