SQL> create undo tablespace undotbs2 datafile '/XXX//undotbs2_01.dbf' size 2048M;


Tablespace created.


SQL> alter system set undo_tablespace='undotbs2' scope=both;


System altered.


SQL> drop tablespace UNDOTBS1 including contents and datafiles;


Tablespace dropped.



SQL> create undo tablespace undotbs1 datafile '/XXX/undotbs1_01.dbf' size 20480M;


Tablespace created.


SQL> alter system set undo_tablespace='undotbs1' scope=both;


System altered.


SQL> show parameter undo


NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
_undo_autotune                       boolean     FALSE
undo_management                      string      AUTO
undo_retention                       integer     10800
undo_tablespace                      string      undotbs1

SQL> alter tablespace undotbs1 add datafile '/XXX/undotbs1_02.dbf' size 20480M;


Tablespace altered.


SQL> select name,value from v$parameter where name in('undo_management','undo_tablespace');


NAME                                                                             VALUE
-------------------------------------------------------------------------------- ---------------------------------------------------
undo_management                                                                  AUTO
undo_tablespace                                                                  undotbs1


SQL> alter tablespace undotbs1 add datafile '/XXX/undotbs1_03.dbf' size 20480M;

Tablespace altered.

 SQL> drop tablespace UNDOTBS2 including contents and datafiles;


Tablespace dropped.