1. 6 Copyright © 2005, Oracle. All rights reserved. Managing Database Storage Structures

2. 6-2 Copyright © 2005, Oracle. All rights reserved. Objectives After completing this lesson, you should be able to do the following: Use Oracle Enterprise Manager to view database storage structures Create new storage structures in a database Reclaim unused space in a database Manage structures used to undo the changes that are made to the database and maintain consistency

3. 6-3 Copyright © 2005, Oracle. All rights reserved. Oracle Database Structures System Monitor SMON Database Writer DBW0 Check- point CKPT Log Writer LGWR Process Monitor PMON Archiver ARC0 SGA Java pool Database buffer cache Redo log buffer Shared pool Large pool Data filesControl filesRedo log files Archived log files

4. 6-4 Copyright © 2005, Oracle. All rights reserved. Exploring the Storage Structure of the Oracle Database Click the links to view detailed information.

5. 6-5 Copyright © 2005, Oracle. All rights reserved. Control File Contains physical database structure information Multiplexed to protect against loss Read at mount stage Control files

6. 6-6 Copyright © 2005, Oracle. All rights reserved. Redo Log Files Record changes to the database Should be multiplexed to protect against loss Redo log buffer Log Writer LGWR Group 1Group 2Group 3

7. 6-7 Copyright © 2005, Oracle. All rights reserved. Multiplexing the Redo Log

8. 6-8 Copyright © 2005, Oracle. All rights reserved. Tablespaces and Data Files Tablespaces comprise one or more data files. Data files belong to only one tablespace. Segments can span data files within a tablespace. USERS Tablespace Data file 1Data file 2

9. 6-9 Copyright © 2005, Oracle. All rights reserved. Tablespaces in the Preconfigured Database SYSTEM : Contains data dictionary tables and other administrative data SYSAUX : Auxiliary tablespace to the SYSTEM tablespace TEMP : Contains transient data that persists only for the duration of the session UNDOTBS1 : Contains undo segments USERS : Is the default tablespace for all objects created by nonsystem users EXAMPLE : Contains the sample schemas

10. 6-10 Copyright © 2005, Oracle. All rights reserved. Full Notes Page

11. 6-11 Copyright © 2005, Oracle. All rights reserved. Enlarging the Database You can enlarge the database in the following ways: Creating a new tablespace Adding a data file to an existing tablespace Increasing the size of a data file Providing for dynamic growth of a data file

12. 6-12 Copyright © 2005, Oracle. All rights reserved. Creating a New Tablespace

13. 6-13 Copyright © 2005, Oracle. All rights reserved. Creating a New Tablespace

14. 6-14 Copyright © 2005, Oracle. All rights reserved. Modifying a Tablespace You can modify a tablespace by: Adding a data file Setting it to automatically extend Manually extending it by increasing the size of a data file Changing its space thresholds Changing its status to offline

15. 6-15 Copyright © 2005, Oracle. All rights reserved. Full Notes Page

16. 6-16 Copyright © 2005, Oracle. All rights reserved. Dropping a Tablespace When you drop a tablespace, the following actions take place: Objects that were stored in the tablespace are removed. Data files are deleted from the operating system.

17. 6-17 Copyright © 2005, Oracle. All rights reserved. Reclaiming Space in a Tablespace You can reclaim available space in your tablespace as follows: Use the Segment Advisor to determine whether there are objects that can be shrunk to free space. Perform the shrink operation to compact segments and return the space to the tablespace.

18. 6-18 Copyright © 2005, Oracle. All rights reserved. Full Notes Page

19. 6-19 Copyright © 2005, Oracle. All rights reserved. Managing Undo Undo records contain a copy of data as it looks before a change is made. Undo is used to undo or roll back uncommitted changes that result from an explicit rollback request or recovery. Undo provides read consistency. Undo enables flashback features. Undo retention periods affect reuse of undo segments.

20. 6-20 Copyright © 2005, Oracle. All rights reserved. Full Notes Page

21. 6-21 Copyright © 2005, Oracle. All rights reserved. Managing Undo Retention Automatic tuning of undo retention: The Oracle database server automatically tunes the undo retention period based on its ongoing monitoring of undo generation. UNDO_RETENTION : Determines the minimum threshold value of undo retention

22. 6-22 Copyright © 2005, Oracle. All rights reserved. Sizing the Undo Tablespace Auto-extensible: Automatic extension of the undo tablespace data file is possible. Fixed-size: Undo tablespace data file is of a fixed size.

23. 6-23 Copyright © 2005, Oracle. All rights reserved. Using Enterprise Manager to Manage Undo

24. 6-24 Copyright © 2005, Oracle. All rights reserved. Using the Undo Advisor

25. 6-25 Copyright © 2005, Oracle. All rights reserved. Full Notes Page

26. 6-26 Copyright © 2005, Oracle. All rights reserved. Summary In this lesson, you should have learned how to: Use Enterprise Manager to view database storage structures Create new storage structures in your database –Multiplex the redo log file –Create and modify tablespaces Use the Segment Advisor and reclaim unused space in your database Manage undo

27. 6-27 Copyright © 2005, Oracle. All rights reserved. Practice 6: Overview This practice covers the following topics: Using Enterprise Manager to view the storage structure of the database Multiplexing the redo log Creating a new tablespace Managing undo in the database

28. 6-28 Copyright © 2005, Oracle. All rights reserved.