How to shrink temp tablespace in oracle?

Question

How can we shrink temp tablespace in oracle? And why it is increasing so much like upto 25 GB since there is only one schema in the database for the application and data table space size is 2 GB and index table space size is 1 GB used.

Answer 1

Oh My Goodness! Look at the size of my temporary table space! Or... how to shrink temporary tablespaces in Oracle.

Yes I ran a query to see how big my temporary tablespace is:

SQL> SELECT tablespace_name, file_name, bytes 2  FROM dba_temp_files WHERE tablespace_name like 'TEMP%';  TABLESPACE_NAME   FILE_NAME                                 BYTES ----------------- -------------------------------- -------------- TEMP              /the/full/path/to/temp01.dbf     13,917,200,000 

The first question you have to ask is why the temporary tablespace is so large. You may know the answer to this off the top of your head. It may be due to a large query that you just run with a sort that was a mistake (I have done that more than once.) It may be due to some other exceptional circumstance. If that is the case then all you need to do to clean up is to shrink the temporary tablespace and move on in life.

But what if you don't know? Before you decide to shrink you may need to do some investigation into the causes of the large tablespace. If this happens on a regular basis then it is possible that your database just needs that much space.

The dynamic performance view

V$TEMPSEG_USAGE 

can be very useful in determining the cause.

Maybe you just don't care about the cause and you just need to shrink it. This is your third day on the job. The data in the database is only 200MiB if data and the temporary tablespace is 13GiB - Just shrink it and move on. If it grows again then we will look into the cause. In the mean time I am out of space on that disk volume and I just need the space back.

Let's take a look at shrinking it. It will depend a little on what version of Oracle you are running and how the temporary tablespace was set up.
Oracle will do it's best to keep you from making any horrendous mistakes so we will just try the commands and if they don't work we will shrink in a new way.

First let's try to shrink the datafile. If we can do that then we get back the space and we can worry about why it grew tomorrow.

SQL> SQL> alter database tempfile '/the/full/path/to/temp01.dbf' resize 256M;  alter database tempfile '/the/full/path/to/temp01.dbf' resize 256M *    ERROR at line 1: ORA-03297: file contains used data beyond requested RESIZE value 

Depending on the error message you may want to try this with different sizes that are smaller than the current site of the file. I have had limited success with this. Oracle will only shrink the file if the temporary tablespace is at the head of the file and if it is smaller than the size you specify. Some old Oracle documentation (they corrected this) said that you could issue the command and the error message would tell you what size you could shrink to. By the time I started working as a DBA this was not true. You just had to guess and re-run the command a bunch of times and see if it worked.

Alright. That didn't work. How about this.

SQL> alter tablespace YOUR_TEMP_TABLESPACE_NAME shrink space keep 256M; 

If you are in 11g (Maybee in 10g too) this is it! If it works you may want to go back to the previous command and give it some more tries.

But what if that fails. If the temporary tablespace is the default temporary that was set up when the database was installed then you may need to do a lot more work. At this point I usually re-evaluate if I really need that space back. After all disk space only costs $X.XX a GiB. Usually I don't want to make changes like this during production hours. That means working at 2AM AGAIN! (Not that I really object to working at 2AM - it is just that... Well I like to sleep too. And my wife likes to have me at home at 2AM... not roaming the downtown streets at 4AM trying to remember where I parked my car 3 hours earlier. I have heard of that "telecommuting" thing. I just worry that I will get half way through and then my internet connectivity will fail - then I have to rush downtown to fix it all before folks show up in the morning to use the database.)

Ok... Back to the serious stuff... If the temporary tablespace you want to shrink is your default temporary tablespace, you will have to first create a new temporary tablespace, set it as the default temporary tablespace then drop your old default temporary tablespace and recreate it. Afterwords drop the second temporary table created.

SQL> CREATE TEMPORARY TABLESPACE temp2 2  TEMPFILE '/the/full/path/to/temp2_01.dbf' SIZE 5M REUSE 3  AUTOEXTEND ON NEXT 1M MAXSIZE unlimited 4  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 2  TEMPFILE '/the/full/path/to/temp01.dbf' SIZE 256M REUSE 3  AUTOEXTEND ON NEXT 128M MAXSIZE unlimited 4  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. 

Hopefully one of these things will help!