DROP UNDO TABLESPACE ACTIVE ROLLBACK SEGMENT

1. SET UNDO_MANG= MANUAL ( INIT.ORA)

2. Comment the entries of the undo segments out of the init.ora file by using the following statement in the init.ora file:

_offline_rollback_segments=(_SYSSMU1$,_SYSSMU2$,_SYSSMU3$,.....)

3) Startup mount pfile='fullpath to pfile'

4) Than drop the datafiles,

sql>Alter Database datafile 'fullpath & filename' offline drop;

5) Alter Database Open;

6) Drop the undo segments,

sql>Drop Rollback Segment RB1;
" "
Drop.. RBn;

7) Drop Tablespace Including Contents;

8)Add the new undo tablespace.

9) Shutdown Immediate;

10) Change the init.ora parameters back to Undo_management = AUTO and modify the parameter Undo_tablespace= and remove the _offline_rollback_segments parameter.

11) Startup the Database