可以创建不同的临时表空间，并加入到同一个tablespace group中：

SQL> alter database tempfile 1 resize 10m;

Database altered.

SQL> select tablespace_name,file_id,file_name,bytes/1024/1024 from dba_temp_files;

TABLESPACE_NAME                   FILE_ID FILE_NAME                                          BYTES/1024/1024
------------------------------ ---------- -------------------------------------------------- ---------------
TEMP1                                   1 /oracle/oradata/ebank/10g_temp01.dbf                            10

SQL> create temporary tablespace temp2 tempfile '/oracle/oradata/ebank/10g_temp02.dbf' size 20m tablespace group tmp_group;

Tablespace created.

此时，创建一个索引：

SQL> create index idx_test on test(empno,ename);
create index idx_test on test(empno,ename)
                         *
ERROR at line 1:
ORA-01652: unable to extend temp segment by 128 in tablespace TEMP1

提示temp1空间不足，此时将temp1加入到tmp_group中，并创建temp3加入到tmp_

SQL> alter tablespace temp1 tablespace group tmp_group;

Tablespace altered.

SQL> ALTER DATABASE default temporary tablespace tmp_group;

Database altered.

SQL> create temporary tablespace temp3 tempfile '/oracle/oradata/ebank/10g_temp03.dbf' size 100m tablespace group tmp_group;

Tablespace created.

此时再创建索引：
SQL> create index idx_test on test(empno,ename);

Index created.

创建成功。可见，通过创建tablespace group，可以很方便的把多个临时表空间组织到一起。