1. Basic Storage Concepts and Settings
Chapter 6
Basic Storage Concepts
and Settings
Oracle9i Database Administrator: Implementation and Administration

2. Oracle9i Database Administrator: Implementation and Administration
Objectives
Differentiate between logical and physical structures
Create many types of tablespaces
Configure and view storage for tablespaces and datafiles
Use undo data
Oracle9i Database Administrator: Implementation and Administration

3. Introduction to Storage Structures
Internal structures store:
The structure of every table, view, and other objects you create
The data you load into your tables and other objects
Information about the structure of tables, views, etc. (metadata)
Oracle9i Database Administrator: Implementation and Administration

4. Introduction to Storage Structures
Physical structures:
Datafiles
Operating system blocks
Redo log files
Control files
Oracle9i Database Administrator: Implementation and Administration

5. Introduction to Storage Structures
Logical Structures:
Data block
Extent
Segment
Schema object
Tablespace
Oracle9i Database Administrator: Implementation and Administration

6. Introduction to Storage Structures
Logical data blocks map directly to contiguous operating system blocks in datafiles
Oracle9i Database Administrator: Implementation and Administration

7. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
Add multiple files, separated by commas if needed
Clause is required for user managed files
Clause is optional when using OMF
Can be used to specify SIZE of OMF file
Note: additional sub-clauses shown later
Oracle9i Database Administrator: Implementation and Administration

8. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
TEMPORARY: This option used only when creating temporary tablespaces that are dictionary-managed.
PERMANENT: Default option; stores permanent objects such as tables and indexes
Oracle9i Database Administrator: Implementation and Administration

9. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
LOCAL: Default; tablespace manages extent free space in a bitmap inside the tablespace
DICTIONARY: tablespace manages extent free space in the data dictionary
Note: additional sub-clauses shown later
Oracle9i Database Administrator: Implementation and Administration

10. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
LOGGING: Default; all DML, DDL, and mass INSERT commands recorded in redo log
NOLOGGING: only DML commands recorded in redo log
Oracle9i Database Administrator: Implementation and Administration

11. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
ONLINE: Default; available for use
OFFLINE: not available for use
Oracle9i Database Administrator: Implementation and Administration

12. Tablespaces and Datafiles
CREATE TABLESPACE <tablespacename>
DATAFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
TEMPORARY|PERMANENT
EXTENT MANAGEMENT LOCAL|DICTIONARY
LOGGING|NOLOGGING
ONLINE|OFFLINE
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
AUTO: Manages segment free space in a bitmap in the tablespace
MANUAL: Manages segment free space in the data dictionary
Oracle9i Database Administrator: Implementation and Administration

13. Implementing OMF With Tablespaces
DB_CREATE_FILE_DEST must be set:
In init<sid>.ora
Or, during session
CREATE TABLESPACE command:
Omit DATAFILE clause in
Or, include DATAFILE clause but only include SIZE clause (omit file name)
Oracle9i Database Administrator: Implementation and Administration

14. Oracle9i Database Administrator: Implementation and Administration
The DATAFILE Clause
DATAFILE '<datafilename>'
SIZE <nn>|REUSE
AUTOEXTEND ON|OFF
MAXSIZE <nn>|UNLIMITED
AUTOEXTEND ON: Allow file to expand when Oracle determines more space is needed
AUTOEXTEND OFF: Do not expand file
SIZE <nn>: Specify size in bytes, kilobytes, or megabytes
REUSE: File already exists
Oracle9i Database Administrator: Implementation and Administration

15. Oracle9i Database Administrator: Implementation and Administration
The DATAFILE Clause
DATAFILE '<datafilename>'
SIZE <nn>|REUSE
AUTOEXTEND ON|OFF
MAXSIZE <nn>|UNLIMITED
Used with AUTOEXTEND ON:
MAXSIZE <nn>: Specify maximum file size in bytes, kilobytes, or megabytes
UNLIMITED: File can grow to limits of operating system
Oracle9i Database Administrator: Implementation and Administration

16. The EXTENT MANAGEMENT and SEGMENT SPACE MANAGEMENT Clauses
Syntax for: EXTENT MANAGEMENT LOCAL:
EXTENT MANAGEMENT LOCAL|DICTIONARY
AUTOALLOCATE|UNIFORM SIZE <nn>
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
MINIMUM EXTENT <nn>
DEFAULT STORAGE (INITIAL <nn> NEXT <nn> PCTINCREASE <nn>
MINEXTENTS <nn> MAXEXTENTS <nn>)
AUTO: Manages segment free space in a bitmap in the tablespace
MANUAL: Manages segment free space in the data dictionary
AUTOALLOCATE: Allow the system to manage extent size for all tables and other objects created in the tablespace
UNIFORM SIZE <nn>: Require the specified extent size for all tables and other objects created in the tablespace
Oracle9i Database Administrator: Implementation and Administration

17. The EXTENT MANAGEMENT and SEGMENT SPACE MANAGEMENT Clauses
Syntax for dictionary-managed tablespace:
EXTENT MANAGEMENT LOCAL|DICTIONARY
SEGMENT SPACE MANAGEMENT MANUAL|AUTO
AUTOALLOCATE|UNIFORM SIZE <nn>
MINIMUM EXTENT <nn>
DEFAULT STORAGE
(INITIAL <nn> NEXT <nn> PCTINCREASE <nn>
MINEXTENTS <nn> MAXEXTENTS <nn>)
Minimum extent size allowed for any object created in the tablespace
Default storage settings for any object created in the tablespace without a STORAGE clause of its own
Oracle9i Database Administrator: Implementation and Administration

18. The EXTENT MANAGEMENT Clause
Example of dictionary-managed datafile
Example: A new table needing 6 M of space skips over the deallocated extents
Coalesce free space periodically to combine deallocated extents
Oracle9i Database Administrator: Implementation and Administration

19. Creating a Dictionary-Managed Tablespace
Example:
CREATE TABLESPACE USER_TEST
DATAFILE 'D:\oracle\data\user_test01.dbf' SIZE 250M
AUTOEXTEND ON
EXTENT MANAGEMENT DICTIONARY
MINIMUM EXTENT 15M
DEFAULT STORAGE (INITIAL 90M NEXT 15M PCTINCREASE 0
MINEXTENTS 1 MAXEXTENTS 50);
Oracle9i Database Administrator: Implementation and Administration

20. Creating a Locally Managed Tablespace
Example of locally managed datafile
All new tables must use extents of the same size or multiples of the size
Example: A new table needing a 10M extent would use the free space from two 5 M deallocated extents
Deallocated extents are automatically coalesced
Oracle9i Database Administrator: Implementation and Administration

21. Creating a Locally Managed Tablespace
Example:
CREATE TABLESPACE USER_AUTO
DATAFILE '<C:oracle\oradata\user_auto01.dbf'
SIZE 20M AUTOEXTEND OFF
EXTENT MANAGEMENT LOCAL AUTOALLOCATE
SEGMENT SPACE MANAGEMENT AUTO;
Oracle9i Database Administrator: Implementation and Administration

22. Segment Types and Their Uses
Data segment: for tables, object tables, triggers
Index segment: for indexes
Temporary segment: for sorting operations and temporary tables
Rollback segment: for undo data
LOB segment: for LOB data stored separately from the rest of the table’s data
Oracle9i Database Administrator: Implementation and Administration

23. Temporary Tablespaces
Oracle recommends creating locally managed temporary tablespaces
Used for temporary segments
Command syntax:
CREATE TEMPORARY TABLESPACE <tablespacename>
TEMPFILE <filename> SIZE <nn> AUTOEXTEND ON|OFF
EXTENT MANAGEMENT LOCAL UNIFORM SIZE <nn>
Oracle9i Database Administrator: Implementation and Administration

24. Tablespaces With Nonstandard Data Block Size
Can be 2 K, 4 K, 8 K, 16 K, or 32 K
Requires a special memory cache that matches the block size
Create cache by setting the appropriate initialization parameter:
DB_2K_CACHE_SIZE
DB_4K_CACHE_SIZE
DB_8K_CACHE_SIZE
DB_16K_CACHE_SIZE
DB_32K_CACHE_SIZE
Oracle9i Database Administrator: Implementation and Administration

25. Tablespaces With Nonstandard Data Block Size
Example:
CREATE TABLESPACE TBS_2K
DATAFILE '<C:\oracle\oradata\tbs_2k.dbf'
SIZE 4M BLOCKSIZE 2K;
Oracle9i Database Administrator: Implementation and Administration

26. Configuring and Viewing Storage
Changes you can make to a tablespace:
LOGGING/NOLOGGING
PERMANENT/TEMPORARY
READ ONLY/READ WRITE
Coalesce contiguous storage space
Add new datafile
Rename a datafile
Change size of a datafile
Oracle9i Database Administrator: Implementation and Administration

27. Configuring and Viewing Storage
Syntax:
ALTER TABLESPACE <tablespacename>
ADD|RENAME DATAFILE <filename>
SIZE <nn> AUTOEXTEND ON|OFF REUSE
DEFAULT STORAGE (INITIAL <nn> NEXT <nn>
PCTINCREASE <nn>
MINEXTENTS <nn> MAXEXTENTS <nn>)
MINIMUM EXTENT <nn>
COALESCE
Oracle9i Database Administrator: Implementation and Administration

28. Configuring and Viewing Storage
Taking a tablespace offline:
Stops it from being accessed by users
Methods for taking a tablespace offline:
NORMAL: default
TEMPORARY: for damaged datafiles
IMMEDIATE: for damaged disk (media)
Oracle9i Database Administrator: Implementation and Administration

29. Read-only Tablespaces
Can only be queried
No inserts, updates, or deletes
Example:
ALTER TABLESPACE ACCOUNTING READ ONLY;
Oracle9i Database Administrator: Implementation and Administration

30. Dropping Tablespaces Syntax: DROP TABLESPACE <tablespacename>
INCLUDING CONTENTS
AND DATAFILES
CASCADE CONSTRAINTS;
Use when there are constraints outside the tablespace that reference this tablespace
Use when there is data in the tablespace
Oracle9i Database Administrator: Implementation and Administration

31. Querying the Data Dictionary For Storage Data
Oracle9i Database Administrator: Implementation and Administration

32. Querying the Data Dictionary For Storage Data
Example:
Find adjacent free extents that should be coalesced
SELECT BLOCK_ID, BLOCK_ID+BLOCKS NEXT_BLOCK_ID, BLOCKS
FROM DBA_FREE_SPACE
WHERE TABLESPACE_NAME = 'USERS'
ORDER BY BLOCK_ID;
Oracle9i Database Administrator: Implementation and Administration

33. Querying the Data Dictionary For Storage Data
Identifying adjacent free sets of blocks
Oracle9i Database Administrator: Implementation and Administration

34. Oracle9i Database Administrator: Implementation and Administration
Overview of Undo Data
Undo data is made of undo blocks
Contain before images of data blocks
Assist in read-consistency
Two methods for managing:
Manual: the old way (with manually created redo segments)
Automatic: the new way (with undo tablespace)
Oracle9i Database Administrator: Implementation and Administration

35. Implementing Automatic Undo Management
Requirements:
Set initialization parameters:
UNDO_MANAGEMENT=AUTO
UNDO_TABLESPACE=<tablespacename>
Create UNDO tablespace:
While creating the database
Later with CREATE UNDO TABLESPACE command
Oracle9i Database Administrator: Implementation and Administration

36. Implementing Automatic Undo Management
Optional initialization parameters:
UNDO_RETENTION: time in seconds that undo data is saved after commit (default is 900 seconds)
UNDO_SURPRESS_ERRORS: defines error handling when transitioning from manual to automatic undo management
Oracle9i Database Administrator: Implementation and Administration

37. Oracle9i Database Administrator: Implementation and Administration
Chapter Summary
Database structures are divided into logical and physical groups
Physical structures include datafiles, control files, and redo log files
Logical structures include tablespaces, extents, and data blocks
A tablespace always has at least one datafile where its data is stored
Locally managed tablespaces use a bitmap to track extent free space
Oracle9i Database Administrator: Implementation and Administration

38. Oracle9i Database Administrator: Implementation and Administration
Chapter Summary
When using OMF, omit the DATAFILE clause in the CREATE TABLESPACE command
AUTOEXTEND ON allows a datafile to grow as needed
Dictionary-managed tablespaces:
Use the data dictionary to track extent free space
Don’t automatically coalesce free space
Locally managed tablespaces:
Automatically coalesce free space
Keep all extents the same size or a variable system- controlled size
Oracle9i Database Administrator: Implementation and Administration

39. Oracle9i Database Administrator: Implementation and Administration
Chapter Summary
Types of segments: data, index, temporary, and rollback
Temporary tablespaces store data while sorting, and temporary tables
Tablespaces can be ONLINE or OFFLINE
A READ ONLY tablespace is not included in regular backups or recoveries
Oracle9i Database Administrator: Implementation and Administration

40. Oracle9i Database Administrator: Implementation and Administration
Chapter Summary
Dropping a tablespace with INCLUDING CONTENTS destroys all its data
Data dictionary views for tablespaces include DBA_TABLESPACES and DBA_FREE_EXTENTS
Undo data gives users read consistency
Automatic undo management uses an UNDO tablespace
Oracle9i Database Administrator: Implementation and Administration