If physically temp file exists, then reuse by adding temp file
alter tablespace temp add tempfile ‘/u01/app/oracle/product/10.2.0/oradata/prod/temp01.dbf’ size 50m reuse;
#Resizing or add new temp file. If not enough space available.
SQL> alter database tempfile ‘/u01/app/oracle/product/10.2.0/oradata/prod/temp01.dbf’ resize 500m;