Drop tablespace tmp1 including contents and datafiles;

1.SELECT TABLESPACE_NAME FROM DBA_TABLESPACES
WHERE CONTENTS='TEMPORARY';

2.SELECT * FROM DATABASE_PROPERTIES where PROPERTY_NAME='DEFAULT_TEMP_TABLESPACE';

3.select username,temporary_tablespace from dba_users;

4.ALTER DATABASE DEFAULT TEMPORARY TABLESPACE <<your temporary tablespace>>

5.select username,temporary_tablespace from dba_users; -- to make sure all users are assigned default temp tablespace.

6.drop other temporary tablespaces listed in step 2.

DROP TABLESPACE <<tablespacename>>
   INCLUDING CONTENTS AND DATAFILES;

CREATE OR REPLACE VIEW temp_sort_user (
   tablespace_name,
   username,
   sid,
   serial_id,
   contents,
   segtype,
   extents,
   blocks,
   bytes )
AS
SELECT
    b.tablespace          tablespace_name
  , a.username            username
  , a.sid                 sid
  , a.serial#             serial_id
  , b.contents            contents
  , b.segtype             segtype
  , b.extents             extents
  , b.blocks              blocks
  , (b.blocks * c.value)  bytes
FROM
    v$session     a
  , v$sort_usage  b
  , (select value from v$parameter
     where name = 'db_block_size') c
WHERE
      a.saddr = b.session_addr
/

SQL> select * from temp_sort_user;