An Essential Guide to Oracle Tablespace Group

Summary: in this tutorial, you will learn about Oracle temporary tablespace group and how to use the tablespace group effectively to optimize internal Oracle operations.

Introduction to Oracle tablespace groups

A tablespace group typically consists of multiple temporary tablespaces. A tablespace group allows a user to consume temporary space from multiple temporary tablespaces, instead of a single temporary tablespace. By using a tablespace group, you can avoid the problem caused when one temporary tablespace does not have enough space to hold the results of a sort.

The following describes the property of a tablespace group:

A tablespace group must contain at least one temporary tablespace.
The name of a tablespace group cannot be the same as any tablespace.
A tablespace group can be assigned as a default temporary tablespace for the database or a temporary tablespace for a user.

Creating a tablespace group

Oracle does not provide a statement to create a tablespace group explicitly. You create a tablespace group when you assign the first temporary tablespace to the group using the CREATE TEMPORARY TABLESPACE statement:

CREATE TEMPORARY TABLESPACE tablespace_name 
    TEMPFILE 'path_to_file'
    SIZE 50M
    TABLESPACE GROUP group_name;
Code language: SQL (Structured Query Language) (sql)

Or ALTER TABLESPACE statement:

ALTER TABLESPACE tablespace_name 
    TABLESPACE GROUP group_name;
Code language: SQL (Structured Query Language) (sql)

Removing a tablespace group

Oracle automatically drops a tablespace group when you remove the last temporary tablespace from the tablespace group.

Viewing tablespace groups

The view DBA_TABLESPACE_GROUPS lists all tablespace groups and their member temporary tablespace.

SELECT * FROM DBA_TABLESPACE_GROUPS;
Code language: SQL (Structured Query Language) (sql)

Moving a tablespace to another tablespace group

To move a temporary tablespace to another tablespace group you use the ALTER TABLESPACE statement. This statement moves the temporary tablespace tablespace_name to the tablespace group destination:

ALTER TABLESPACE tablespace_name
TABLESPACE GROUP destination;
Code language: SQL (Structured Query Language) (sql)

Note that the destination tablespace group must exist.

Assigning a tablespace group as the default temporary tablespace

To assign a tablespace group as the default temporary tablespace for a database, you use the ALTER DATABASE DEFAULT TEMPORARY TABLESPACE statement:

ALTER DATABASE DEFAULT TEMPORARY TABLESPACE tablespace_group;
Code language: SQL (Structured Query Language) (sql)

All users who have not been assigned a temporary tablespace will use the temporary tablespaces contained in the tablespace_group.

Note that you cannot drop any temporary tablespace that belongs to a tablespace group which is specified as a default temporary tablespace. In this case, you first need to de-assign the temporary tablespace from the tablespace group and then remove it.

Benefits of using a tablespace group

A tablespace group brings the following benefits:

Enable multiple default temporary tablespaces to be used at the database level.
Allow the user to use multiple temporary tablespaces in different sessions at the same time.
Reduce the contention in case you have multiple temporary tablespaces.

Oracle tablespace group examples

First, create a new temporary tablespace and assign it to the tablespace group tbs1:

CREATE TEMPORARY TABLESPACE temp2 
TEMPFILE 'temp2.dbf' 
SIZE 100M 
TABLESPACE GROUP tbsg1;
Code language: SQL (Structured Query Language) (sql)

Because the tablespace group tbsg1 has not existed, the statement also created the tablespace group tbsg1.

Second, assign the temp temporary tablespace temp to the tbsg1 tablespace group:

ALTER TABLESPACE temp TABLESPACE GROUP tbsg1;
Code language: SQL (Structured Query Language) (sql)

Third, assign the tablespace group gbsg1 as the default temporary tablespace:

ALTER DATABASE DEFAULT TEMPORARY TABLESPACE tbsg1;
Code language: SQL (Structured Query Language) (sql)

Finally, verify the current default temporary tablespace:

SELECT 
    property_name, 
    property_value 
FROM 
    database_properties 
WHERE 
    property_name='DEFAULT_TEMP_TABLESPACE';
Code language: SQL (Structured Query Language) (sql)

In this tutorial, you have learned about the Oracle tablespace group and how to use tablespace group effectively to optimize internal Oracle operations.

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