Resizing Temporary Table space

Before resize the temp table space make sure your   usage of the temp space following quarry can be use for find out the usage

SELECT A.tablespace_name tablespace, D.mb_total,
SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_used,
D.mb_total - SUM (A.used_blocks * D.block_size) / 1024 / 1024 mb_free
FROM v$sort_segment A,
(
SELECT B.name, C.block_size, SUM (C.bytes) / 1024 / 1024 mb_total
FROM v$tablespace B, v$tempfile C
WHERE B.ts#= C.ts#
GROUP BY B.name, C.block_size
) D
WHERE A.tablespace_name = D.name
GROUP by A.tablespace_name, D.mb_total;

Output should be as

TABLESPACE                        MB_TOTAL    MB_USED    MB_FREE

------------------------------- ---------- ---------- ----------

TEMP2                                 1024          0             1024

TEMP1                                 1024          .125         1023.875

Here we can reduce up to   100mb because currently it use only .125mb or you can  increase as your  requirement

SQL> alter database tempfile '/u02/oradata/TESTDB/temp01.dbf' resize 100M;

SQL> alter database tempfile '/u02/oradata/TESTDB/temp01.dbf' resize 2G;