Week 10-11 Managing Tablespaces and Data Files.ppt

Copyright © Oracle Corporation, 2001. All rights reserved.
Managing Tablespaces and Datafiles

8-2 Copyright © Oracle Corporation, 2001. All rights reserved.
Objectives
After completing this lesson, you should be able to do
the following:
• Define the purpose of tablespaces and datafiles
• Create tablespaces
• Manage tablespaces
• Create and manage tablespaces using Oracle
Managed Files (OMF)

Tablespaces and Datafiles
Oracle stores data logically in tablespaces and
physically in datafiles.
• Tablespaces:
– Can belong to only one database at a time
– Consist of one or more datafiles
– Are further divided into logical units of storage
• Datafiles:
– Can belong to only one
tablespace and one database
– Are a repository for schema
object data
Database
Tablespace
Datafiles

Types of Tablespaces
• SYSTEM tablespace
– Created with the database
– Contains the data dictionary
– Contains the SYSTEM undo segment
• Non-SYSTEM tablespace
– Separate segments
– Eases space administration
– Controls amount of space allocated to a user

Creating Tablespaces
CREATE TABLESPACE userdata
DATAFILE '/u01/oradata/userdata01.dbf' SIZE 100M
AUTOEXTEND ON NEXT 5M MAXSIZE 200M;
A tablespace is created using the command:
CREATE TABLESPACE

Space Management in Tablespaces
• Locally managed tablespace:
– Free extents managed in the tablespace
– Bitmap is used to record free extents
– Each bit corresponds to a block or group of blocks
– Bit value indicates free or used
• Dictionary-managed tablespace:
– Free extents are managed by the data dictionary
– Appropriate tables are updated when extents are
allocated or deallocated

Locally Managed Tablespaces
• Reduced contention on data dictionary tables
• No undo generated when space allocation or
deallocation occurs
• No coalescing required
DATAFILE '/u01/oradata/userdata01.dbf' SIZE 500M
EXTENT MANAGEMENT LOCAL UNIFORM SIZE 128K;

Dictionary-Managed Tablespaces
• Extents are managed in the data dictionary
• Each segment stored in the tablespace can have a
different storage clause
• Coalescing required
DATAFILE '/u01/oradata/userdata01.dbf'
SIZE 500M EXTENT MANAGEMENT DICTIONARY
DEFAULT STORAGE
(initial 1M NEXT 1M PCTINCREASE 0);

Undo Tablespace
• Used to store undo segments
• Cannot contain any other objects
• Extents are locally managed
• Can only use the DATAFILE and EXTENT
MANAGEMENT clauses
CREATE UNDO TABLESPACE undo1
DATAFILE '/u01/oradata/undo01.dbf' SIZE 40M;

Temporary Tablespaces
• Used for sort operations
• Cannot contain any permanent objects
• Locally managed extents recommended
CREATE TEMPORARY TABLESPACE temp
TEMPFILE '/u01/oradata/temp01.dbf' SIZE 500M
EXTENT MANAGEMENT LOCAL UNIFORM SIZE 4M;

Default Temporary Tablespace
• Specifies a database-wide default temporary
tablespace
• Eliminates using SYSTEM tablespace for storing
temporary data
• Can be created by using:
– CREATE DATABASE
– Locally managed
– ALTER DATABASE
ALTER DATABASE
DEFAULT TEMPORARY TABLESPACE temp;

Creating a Default Temporary Tablespace
• During database creation:
CREATE DATABASE DBA01
LOGFILE
GROUP 1 ('/$HOME/ORADATA/u01/redo01.log') SIZE 100M,
GROUP 2 ('/$HOME/ORADATA/u02/redo02.log') SIZE 100M,
MAXLOGFILES 5
MAXLOGMEMBERS 5
MAXLOGHISTORY 1
MAXDATAFILES 100
MAXINSTANCES 1
DATAFILE '/$HOME/ORADATA/u01/system01.dbf' SIZE 325M
UNDO TABLESPACE undotbs
DATAFILE '/$HOME/ORADATA/u02/undotbs01.dbf' SIZE 200
DEFAULT TEMPORARY TABLESPACE temp
TEMPFILE '/$HOME/ORADATA/u03/temp01.dbf' SIZE 4M
CHARACTER SET US7ASCII

Creating a Default Temporary Tablespace
• After database creation:
• To find the default temporary tablespace for the
database query DATABASE_PROPERTIES
ALTER DATABASE
DEFAULT TEMPORARY TABLESPACE default_temp2;
SELECT * FROM DATABASE_PROPERTIES;

Restrictions on Default Temporary
Tablespace
Default temporary tablespaces cannot be:
• Dropped until after a new default is made available
• Taken offline
• Altered to a permanent tablespace

Read Only Tablespaces
• Use the following command to place a tablespace in
read only mode
– Causes a checkpoint
– Data available only for read operations
– Objects can be dropped from tablespace
ALTER TABLESPACE userdata READ ONLY;

Taking a Tablespace Offline
• Not available for data access
• Tablespaces that cannot be taken offline:
– SYSTEM tablespace
– Tablespaces with active undo segments
– Default temporary tablespace
• To take a tablespace offline:
• To bring a tablespace online:
ALTER TABLESPACE userdata OFFLINE;
ALTER TABLESPACE userdata ONLINE;

Changing Storage Settings
• Using ALTER TABLESPACE command to change
storage settings:
• Storage settings for locally managed tablespaces
cannot be altered.
ALTER TABLESPACE userdata MINIMUM EXTENT 2M;
ALTER TABLESPACE userdata
DEFAULT STORAGE (INITIAL 2M NEXT 2M
MAXEXTENTS 999);

Resizing a Tablespace
A tablespace can be resized by:
• Changing the size of a datafile:
– Automatically using AUTOEXTEND
– Manually using ALTER TABLESPACE
• Adding a datafile using ALTER TABLESPACE

Enabling Automatic Extension
of Datafiles
• Can be resized automatically with the following
commands:
– CREATE DATABASE
– CREATE TABLESPACE
– ALTER TABLESPACE … ADD DATAFILE
• Example:
• Query the DBA_DATA_FILES view to determine
whether AUTOEXTEND is enabled.
CREATE TABLESPACE user_data
DATAFILE
'/u01/oradata/userdata01.dbf' SIZE 200M
AUTOEXTEND ON NEXT 10M MAXSIZE 500M;

Manually Resizing a Datafile
• Manually increase or decrease a datafile size using
ALTER DATABASE
• Resizing a datafile adds more space without adding
more datafiles
• Manual resizing of a datafile reclaims unused space
in database
• Example:
ALTER DATABASE
RESIZE 200M;

Adding Datafiles to a Tablespace
• Increases the space allocated to a tablespace by
adding additional datafiles
• ADD DATAFILE clause is used to add a datafile
• Example:
ALTER TABLESPACE user_data
ADD DATAFILE '/u01/oradata/userdata03.dbf'
SIZE 200M;

Methods for Moving Datafiles
• ALTER TABLESPACE
– Tablespace must be offline
– Target datafiles must exist
• Steps to rename a datafile:
– Take the tablespace offline.
– Use an OS command to move or copy the files.
– Execute the ALTER TABLESPACE RENAME DATAFILE
command.
– Bring the tablespace online.
– Use an OS command to delete the file if necessary.
ALTER TABLESPACE userdata RENAME
TO '/u02/oradata/userdata01.dbf';

Methods for Moving Datafiles
• ALTER DATABASE
– Database must be mounted
– Target datafile must exist
ALTER DATABASE RENAME
FILE '/u01/oradata/system01.dbf'
TO '/u03/oradata/system01.dbf';

Dropping Tablespaces
• Cannot drop a tablespace if it:
– Is the SYSTEM tablespace
– Has active segments
• INCLUDING CONTENTS drops the segments
• INCLUDING CONTENTS AND DATAFILES deletes
datafiles
• CASCADE CONSTRAINTS drops all referential
integrity constraints
DROP TABLESPACE userdata
INCLUDING CONTENTS AND DATAFILES;

Managing Tablespaces Using OMF
• Define the DB_CREATE_FILE_DEST parameter in one
of the following ways:
– Initialization parameter file
– Set dynamically using ALTER SYSTEM command
• When creating the tablespace:
– Datafile is automatically created and located in
DB_CREATE_FILE_DEST
– Default size is 100 MB
– AUTOEXTEND is set to UNLIMITED
ALTER SYSTEM SET
db_create_file_dest = '/u01/oradata/dba01';

Managing Tablespaces with OMF
• Creating an OMF tablespace:
• Adding an OMF datafile to an existing tablespace:
• Dynamically changing default file location:
• Dropping a tablespace includes deleting OS files:
CREATE TABLESPACE text_data DATAFILE SIZE 20M;
ALTER TABLESPACE text_data ADD DATAFILE;
ALTER SYSTEM SET
db_create_file_dest = '/u01/oradata/dba01';

Obtaining Tablespace Information
Obtaining tablespace and datafile information can be
obtained by querying the following:
• Tablespaces:
– DBA_TABLESPACES
– V$TABLESPACE
• Datafile information:
– DBA_DATA_FILES
– V$DATAFILE
• Temp file information:
– DBA_TEMP_FILES
– V$TEMPFILE

Summary
In this lesson, you should have learned how to:
• Use tablespaces to separate data
• Create various types of tablespaces
• Manage tablespaces
• Manage tablespaces using OMF

Practice 8 Overview
This practice covers the following topics:
• Creating tablespaces
• Modifying tablespaces
• Configuring for and creating a tablespace using
OMF

Week 10-11 Managing Tablespaces and Data Files.ppt

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