1
Lecture 4
ORACLE
TABLESPACES
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Storage Structures
Logical
• A database is divided
into logical storage
units called
tablespaces.
•Each tablespace has
many logical Oracle
data blocks with
DB_BLOCK_SIZE
parameters
Physical
Database
Tablespace
OS file
Segment
Extent
Oracle data
block
OS
block
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How Table Data Is Stored
Columns
Table A
Blocks
Table B
Rows
Segment
Segment
Table
Tablespace
Row piece
Extent
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Anatomy of a Database Block
Data blocks contain the
following:
1. Block header (segment type,
data block address, table Growth
directory, row directory, and
transaction slots of size 23
bytes each)
2. Row data (actual data for the
rows in the block)
3. Free space (middle of the
block )
Block
header
Free
space
Row
data
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Tablespaces and Data Files
• The Oracle database stores data logically in
tablespaces and physically in data files.
• Tablespaces:
• Can belong to only one database
• Consist of one or more data files
• Are further divided into logical units of storage
• Data files:
Database
• Can belong to only one
Tablespace
tablespace and one database
• Are a repository for schema
object data
Data files
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Oracle Managed Files (OMF)
• Specify file operations in terms of database objects rather than file
names.(Tablespaces , Redo log files, Control files, Archived logs,
Block change tracking files, Flashback logs, RMAN) backups)
Parameter
Description
DB_CREATE_FILE_DEST
Defines the location of the default file system
directory for data files and temporary files
DB_CREATE_ONLINE_LOG_
Defines the location for redo log files and
control file creation
DEST_n
DB_RECOVERY_FILE_DEST
Defines the location for RMAN backups
Example:
SQL> ALTER SYSTEM SET DB_CREATE_FILE_DEST =
'/Emam/oradata';
SQL> CREATE TABLESPACE tbs_1;
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Space Management in Tablespaces
1- Locally managed tablespace:
• Free extents are managed in the tablespace.
• A bitmap is used to record free extents.
• Each bit corresponds to a block or group of blocks.
• The bit value indicates free or used extents.
• The use of locally managed tablespaces is recommended.
2- Dictionary-managed tablespace:
• Free extents are managed by the data dictionary.
• Appropriate tables are updated when extents are allocated
or unallocated.
• These tablespaces are supported only for backward
compatibility.
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Tablespaces Prerequisites
• You must have the CREATE TABLESPACE system
privilege.
• To create the SYSAUX tablespace, you must have the
SYSDBA system privilege.
• Before you can create a tablespace, you must create a
database to contain it, and the database must be open.
• You need to define Datafile location by
DB_CREATE_FILE_DEST parameter and with size
100 MB.
• Name of datafile will be similar to
"ora_applicat_abcdefgh000.dbf"
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Exploring the Storage Structure
Click the links to view
detailed information.
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Creating a New Tablespace
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Storage for Locally Managed Tablespaces
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Tablespaces Syntax
• CREATE [ BIGFILE | SMALLFILE ] {
permanent_tablespace_clause |
temporary_tablespace_clause |
undo_tablespace_clause } ;
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Permanent Tablespace
• { MINIMUM EXTENT integer [
K | M ] | BLOCKSIZE integer [ K
] | logging_clause | FORCE
LOGGING | DEFAULT [
table_compression ] storage_clause
| { ONLINE | OFFLINE } |
extent_management_clause |
segment_management_clause |
flashback_mode_clause [
MINIMUM EXTENT integer [ K
| M ] | BLOCKSIZE integer [ K ] |
logging_clause | FORCE
LOGGING | DEFAULT [
table_compression ] storage_clause
| { ONLINE | OFFLINE } |
extent_management_clause |
segment_management_clause |
flashback_mode_clause ]... }
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BIGFILE | SMALLFILE
• A bigfile tablespace contains only one datafile or tempfile,
which can contain up to 232 or 4G blocks. The maximum size
of the single datafile or tempfile is 128 terabytes (TB) for a
tablespace with 32K blocks and 32TB for a tablespace with
8K blocks.
• A smallfile tablespace is a traditional Oracle tablespace,
which can contain 1022 datafiles or tempfiles, each of which
can contain up to 222 or 4M blocks.
• If you omit this clause, then Oracle Database uses the current
default tablespace type of permanent or temporary tablespace
set for the database.
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BLOCKSIZE
• BLOCKSIZE : By Default blocksize define in the parameter
DB_BLOCK_SIZE.
• DEFAULT STORAGE :
• INITIAL – Specifies the size of the object's first extent.3 k
minmum for Locally and 2 k minimum Dictionary.
• NEXT – Specifies the size of the object's sucessive extent.
• PCTINCREASE – Specifies the ratio of the third or the
preceding extent of the object. The default value for
PCTINCREASE is 50 % and the minimum value is 0%.
• MINEXTENTS – The total number of extent allocated to
the segment at the time of creation
• MAXEXTENTS – The maximum number of extent that can
be allocated to the segment .
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EXTENT
• MININUM EXTENT : The extent are multiple of the
size specified in this clause .NEXT and INITIAL extent
size specified should be multiple of minmum extent.
• PERMANENT / TEMPORARY : Permannent is
default, use to store the table,index etc. Temporary is
for temporay segments can not store table,index in
temporary tablespace.
• LOGGING / NOLOGGING : Logging is default,the
DDL operation & direct insert load are recorded in the
redo log file.
• ONLINE / OFFLINE : Online is default,tablespace is
available as soon as created.
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Create Tablespace Examples
1- Creating a Bigfile Tablespace: The following example creates a bigfile tablespace
bigtbs_01 with a datafile bigtbs_f1.dat of 10 MB:
CREATE BIGFILE TABLESPACE bigtbs_01
DATAFILE 'bigtbs_f1.dat'
SIZE 20M AUTOEXTEND ON;
2- Creating an Undo Tablespace: The following example creates a 10 MB undo
tablespace undots1:
CREATE UNDO TABLESPACE undots1
DATAFILE 'undotbs_1a.f'
SIZE 10M AUTOEXTEND ON
RETENTION GUARANTEE;
3- Creating a Temporary Tablespace: The serves assumes as the default
temporary tablespace for database users in the sample database was created:
CREATE TEMPORARY TABLESPACE temp_demo
TEMPFILE 'temp01.dbf' SIZE 5M AUTOEXTEND ON;
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Tablespaces in the Preconfigured Database
SYSTEM
SYSAUX
TEMP
UNDOTBS1
USERS
EXAMPLE
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Tablespaces in the Preconfigured Database
1. SYSTEM : used by the Oracle server to manage the
database and it contains the data dictionary and tables that
contain administrative information about the database.
2. SYSAUX : This is an auxiliary tablespace to the
SYSTEM tablespace. now use the SYSAUX tablespace.
Every Oracle Database10g or later release must have a
SYSAUX tablespace.
3. TEMP
4. UNDOTBS1
5. USERS
6. EXAMPLE
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Actions with Tablespaces
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Viewing Tablespace Information
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Assign tablespaces to users
• Users cannot create objects in a tablespace (even it's their
default tablespace) unless they have a quota on it (or
UNLIMITED TABLESPACE privilege).
• Grant user Emam access to use all space in the tools
tablespace:
1. CREATE TABLESPACE tools DATAFILE
‘/orcl/tools/file_1.dbf' SIZE 100M;
2. ALTER USER Emam QUOTA UNLIMITED ON tools;
3. ALTER USER scott QUOTA 0 ON system;
• Prevent user scott from using space in the system
tablespace:
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Altering a Tablespace
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Altering a Tablespace
•After you create a tablespace, you can later alter it in
several ways as the needs of your system change.
• Renaming
• Changing the status : A tablespace can be in one of
the following statuses .
•Read Write (The tablespace is online and can be
read from and written to).
•Read Only ( Specify read-only to place the
tablespace in transition read-only mode.
•The tablespace is online while in the read-only state.
•You cannot make the SYSTEM or SYSAUX
tablespace read-only.
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ALTER TABLESPACE
•Use the ALTER TABLESPACE statement to alter an existing
tablespace or one or more of its datafiles or tempfiles.
•To alter the SYSAUX tablespace, you must have the SYSDBA
system privilege.
•If you have ALTER TABLESPACE system privilege
•If you have MANAGE TABLESPACE system privilege, then you
can only perform the following operations:
1. Take the tablespace online or offline
2. Begin or end a backup
3. Make the tablespace read only or read write
4. Before you can make a tablespace read only, the following
conditions must be met: The tablespace must be online.
The tablespace must not be involved in an open backup.
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ALTER Syntax
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ALTER Syntax Cont.
ALTER TABLESPACE tablespace { DEFAULT [
table_compression ] storage_clause | MINIMUM
EXTENT integer [ K | M ] | RESIZE size_clause |
COALESCE | RENAME TO
new_tablespace_name | { BEGIN | END }
BACKUP | datafile_tempfile_clauses |
tablespace_logging_clauses |
tablespace_group_clause | tablespace_state_clauses |
autoextend_clause | flashback_mode_clause |
tablespace_retention_clause } ;
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ALTER Examples
Rename the datafile using an ALTER TABLESPACE statement with
the RENAME DATAFILE clause:
ALTER TABLESPACE tbs_02 RENAME DATAFILE
'diskb:tbs_f5.dat' TO 'diska:tbs_f5.dat';
Bring the tablespace back online using an ALTER TABLESPACE
statement with the ONLINE clause:
ALTER TABLESPACE tbs_02 ONLINE;
To adds a datafile to the tablespace
ALTER TABLESPACE tbs_03 ADD DATAFILE 'tbs_f04.dbf' SIZE
100K AUTOEXTEND ON NEXT 10K MAXSIZE 100K;
To change the extent size to 128K:
ALTER TABLESPACE tbs_03 MINIMUM EXTENT 128K;
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Gathering Storage Information
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Viewing Tablespace Contents
• 12061_1_sel_ts_3
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Dropping Tablespaces
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DROP TABLESPACE
•DROP TABLESPACE used the DROP TABLESPACE
from the database.
•Oracle Database does not place it in the recycle bin.
•Therefore, you cannot subsequently either purge or
undrop the tablespace.
•You must have the DROP TABLESPACE system
privilege.
•You cannot drop a tablespace if it contains any rollback
segments holding active transactions.
•You cannot drop the SYSTEM tablespace but can drop
the SYSAUX tablespace
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Restrictions on Dropping Tablespaces
1. You cannot drop a tablespace that contains a domain index or
any objects created by a domain index.
2. You cannot drop an undo tablespace if it is being used by any
instance or if it contains any undo data needed to roll back
uncommitted transactions.
3. You cannot drop a tablespace that has been designated as the
default tablespace for the database.
4. You must first reassign another tablespace as the default
tablespace and then drop the old default tablespace.
5. You cannot drop a temporary tablespace if it is part of the
database default temporary tablespace group. You must first
remove the tablespace from the database default temporary
tablespace group and then drop it.
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DROP TABLESPACE Syntax
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DROP TABLESPACE Example
•To drops tbs_01 tablespace and drops all referential
integrity constraints that refer to primary and unique
keys inside tbs_01:
DROP TABLESPACE tbs_01 INCLUDING
CONTENTS CASCADE CONSTRAINTS;
•To drops the tbs_01 tablespace and deletes all
associated operating system datafiles
DROP TABLESPACE tbs_01 INCLUDING
CONTENTS AND DATAFILES;
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Actions with Tablespaces
1. Add Datafile
2. Create Like
3. Generate DDL
4. Make Locally Managed if the tablespace is currently
dictionary managed.
5. Make Readonly
6. Make Writable
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Making a Tablespace Read-Only
•All tablespaces are initially created as read/write.
•Use the READ ONLY clause in the ALTER TABLESPACE
statement to change a tablespace to read-only.
•You must have the ALTER TABLESPACE or MANAGE
TABLESPACE system privilege.
• The tablespace must be online. This is necessary to ensure that
there is no undo information that needs to be applied to the
tablespace.
•The tablespace must not currently be involved in an online
backup, because the end of a backup updates the header file of
all datafiles in the tablespace.
ALTER TABLESPACE tabelspace_name READ ONLY;
•Once the statement is issued, no transactions are allowed to
make further changes to the tablespace being made read-only.
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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 the dynamic growth of a data file
Database
SYSTEM
tablespace
INVENTORY
tablespace
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Automatic Storage Management(ASM)
• ASM provides a vertical integration
of the file system for single
symmetric multiprocessing (SMP)
machines or on Oracle Real
Application Clusters (RAC) support.
• Automatic Storage Management
• Is a portable and highperformance cluster file system
• Manages Oracle database files
• Spreads data across disks
to balance load
• Mirrors data & Solves many
storage management challenges
Application
Database
File
system
Volume
manager
ASM
Operating system
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ASM: Key Features and Benefits
ASM
Stripes files, but not logical volumes
Provides online disk reconfiguration and
dynamic rebalancing
Allows for adjustable rebalancing speed
Provides redundancy on a per-file basis
Supports only Oracle database files
Is cluster aware
Is automatically installed
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ASM Concepts
ASM
disk group
Database
Tablespace
Data file
Segment
Extent
Oracle data
block
ASM file
ASM disk
File system
file
or
raw device
Allocation unit
Physical
block
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