Switch undo tablespace

Question

Hello,
I created a new undo tablespace and have successfully switched the database to use the new undo tablespace. Now I want to drop the old undo tablespace.
What is the process for me to drop the old undo tablespace?
Is it drop tablespace undotabsOLD; ? What are the 'gotachas' I should be aware before drop a tablespace that was unsed as an undo tablespace? Thank you in advance.

Answer 1

undo_retention is not a 'gotcha' in this case,
according the Oracle document I posted earlier,
the undo tablespace is ready to be dropped when all active transactions gone. It will not wait for undo_retention
see following examples,
--Make a bigger retention just in case
SQL> show parameter undo
NAME                                 TYPE        VALUE
undo_management                      string      AUTO
undo_retention                       integer     3600
undo_tablespace                      string      UNDOTBS_01
-- Now create a new undo
SQL> CREATE UNDO TABLESPACE undotbs_02
  2   DATAFILE '/u02/oradata/undo/undo2.dbf' SIZE 100M REUSE AUTOEXTEND ON
  3  /
Tablespace created.
--  Before we switch make an uncommited transaction on other session
--  Then
SQL> ALTER SYSTEM SET UNDO_TABLESPACE = undotbs_02;
System altered.
SQL> show parameter undo
NAME                                 TYPE        VALUE
undo_management                      string      AUTO
undo_retention                       integer     3600
undo_tablespace                      string      UNDOTBS_02
-- Try to drop UNDOTBS_01
SQL> drop tablespace UNDOTBS_01 including contents and datafiles
  2  /
drop tablespace UNDOTBS_01 including contents and datafiles
ERROR at line 1:
ORA-30013: undo tablespace 'UNDOTBS_01' is currently in use
-- Run a query to list PENDING OFFLINE rollback segments
SQL> SELECT NAME, XACTS "ACTIVE TRANSACTIONS"
  2        FROM V$ROLLNAME, V$ROLLSTAT
  3        WHERE STATUS = 'PENDING OFFLINE'
  4          AND V$ROLLNAME.USN = V$ROLLSTAT.USN;
NAME                           ACTIVE TRANSACTIONS
_SYSSMU10$                                       1
-- Now commit on other session
SQL> select sysdate from dual
  2  /
SYSDATE
2007-06-21 03:49:49
SQL> SELECT NAME, XACTS "ACTIVE TRANSACTIONS"
  2        FROM V$ROLLNAME, V$ROLLSTAT
   3       WHERE STATUS = 'PENDING OFFLINE'
  4          AND V$ROLLNAME.USN = V$ROLLSTAT.USN;
NAME                           ACTIVE TRANSACTIONS
_SYSSMU10$                                       0
-- Wait a few seconds
SQL> select sysdate from dual;
SYSDATE
2007-06-21 03:50:00
SQL> SELECT NAME, XACTS "ACTIVE TRANSACTIONS"
  2    FROM V$ROLLNAME, V$ROLLSTAT
  3   WHERE STATUS = 'PENDING OFFLINE'
  4   AND V$ROLLNAME.USN = V$ROLLSTAT.USN;
no rows selected
-- NOW, drop the tablespace
SQL> drop tablespace UNDOTBS_01 including contents and datafiles;
Tablespace dropped.
Done