SELECT param2.inst_id, inst.instance_number, inst.instance_name, param2.value, param2.issys_modifiable, param2.ordinal FROM gv$parameter2 param2 JOIN gv$instance inst ON inst.inst_id=param2.inst_id
  2  WHERE name='undo_tablespace';

   INST_ID INSTANCE_NUMBER INSTANCE_N VALUE      ISSYS_MODI    ORDINAL
---------- --------------- ---------- ---------- ---------- ----------
         1               1 svcrmdb    UNDOTBS1   IMMEDIATE           1

SYS@11.2.0.4 svcrmdb>
SYS@11.2.0.4 svcrmdb>select tablespace_name from dba_tablespaces where contents='UNDO' ORDER BY tablespace_name;

TABLESPACE_NAME
------------------------------
UNDOTBS1
UNDOTBS2

DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES
ORA-604 signalled during: DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES...
[orac

SYS@11.2.0.4 svcrmdb>DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES;
DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1 
ORA-00942: table or view does not exist 

DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES
ORA-604 signalled during: DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES...