Tuesday, October 21, 2008

Resizing Temporary Tablespace

In many database configurations, the DBA will choose to allow their temporary tablespace (actually the tempfile(s) for the temporary tablespace) to autoextend. A runaway query or sort can easily chew up valuable space on the disk as the tempfiles(s) extends to accommodate the request for space. If the increase in size of the temporary tablespace (the tempfiles) gets exceedingly large because of a particular anomaly, the DBA will often want to resize the temporary tablespace to a more reasonable size in order to reclaim that extra space. The obvious action would be to resize the tempfiles using the following statement:

SQL> alter database tempfile '/u02/oradata/TESTDB/temp01.dbf' resize 250M;
alter database tempfile '/u02/oradata/TESTDB/temp01.dbf' resize 250M
*
ERROR at line 1:
ORA-03297: file contains used data beyond requested RESIZE value

Ouch. You next bounce the database and attempt the same statement only to be greeted with the same error!

Several methods exist to reclaim the used space used for a larger than normal temporary tablespace depending on which release of Oracle you are running. The method that exists for all releases of Oracle is to simply drop and recreate the temporary tablespace back to its original (or another reasonable) size. If you are using Oracle9i or higher, you can apply another method which is to drop the large tempfile (which will drop the tempfile from the data dictionary AND the O/S file system) using the alter database tempfile '' drop including datafiles; command. Each method is explained below.


Dropping / Recreating Temporary Tablespace Method



Keep in mind that the procedures documented here for dropping and recreating your temporary tablespace should be performed during off hours with no users logged on performing work.

If you are working with a temporary tablespace in Oracle8i or a temporary tablespace in Oracle9i that is NOT the default temporary tablespace for the database, this process is straight forward. Simply drop and recreate the temporary tablespace:

SQL> DROP TABLESPACE temp;

Tablespace dropped.

SQL> CREATE TEMPORARY TABLESPACE TEMP
TEMPFILE '/u02/oradata/TESTDB/temp01.dbf' SIZE 500M REUSE
AUTOEXTEND ON NEXT 100M MAXSIZE unlimited EXTENT MANAGEMENT LOCAL UNIFORM SIZE 1M;

Tablespace created.


Oracle9i OR Above Default Temporary Tablespace



The procedures above document how to drop a temporary tablespace that is not the default temporary tablespace for the database. You will know fairly quickly if the tablespace is a default temporary tablespace when you are greeted with the following exception:

SQL> DROP TABLESPACE temp;
drop tablespace temp
*
ERROR at line 1:
ORA-12906: cannot drop default temporary tablespace

In cases where the temporary tablespace you want to resize (using the drop/recreate method) is the default temporary tablespace for the database, you have several more steps to perform, all documented below. The first step you need to perform is create another temporary tablespace (lets call it TEMP2). Next step is making TEMP2 the default temporary tablespace for the database. Drop / recreate the TEMP tablespace to the size you want. Finally, make the newly created TEMP tablespace your default temporary tablespace for the database and drop the TEMP2 tablespace. A full example session is provided below:

SQL> CREATE TEMPORARY TABLESPACE temp2
TEMPFILE '/u02/oradata/TESTDB/temp2_01.dbf' SIZE 5M REUSE
AUTOEXTEND ON NEXT 1M MAXSIZE unlimited
EXTENT MANAGEMENT LOCAL UNIFORM SIZE 1M;

Tablespace created.


SQL> ALTER DATABASE DEFAULT TEMPORARY TABLESPACE temp2;

Database altered.


SQL> DROP TABLESPACE temp INCLUDING CONTENTS AND DATAFILES;

Tablespace dropped.

SQL> CREATE TEMPORARY TABLESPACE temp
TEMPFILE '/u02/oradata/TESTDB/temp01.dbf' SIZE 500M REUSE
AUTOEXTEND ON NEXT 100M MAXSIZE unlimited
EXTENT MANAGEMENT LOCAL UNIFORM SIZE 1M;

Tablespace created.


SQL> ALTER DATABASE DEFAULT TEMPORARY TABLESPACE temp;

Database altered.


SQL> DROP TABLESPACE temp2 INCLUDING CONTENTS AND DATAFILES;

Tablespace dropped.


Related Topic :
  1. Move Datafiles


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