Dropping an Old UNDO with ORA-01548

Problem Description:

Drop undo tablespace fails with error Ora-01548 .
SQL> drop Tablespace UNDOTBS;
drop Tablespace UNDOTBS
*
ERROR at line 1:
ORA-01548: active rollback segment ‘_SYSSMU1$’ found, terminate dropping
tablespace

Cause of The Problem
An attempt was made to drop a tablespace that contains active rollback segments.

Solution of The Problem:
In order to get rid of this error you have to follow following steps.

1)Create pfile if you started with database with spfile.
SQL>Create PFILE from SPFILE;

2)Edit pfile and set undo management to manual.
undo_management = manual

3)Put the entries of the undo segments in the pfile by using the following statement in the pfile:

select segment_name,status,tablespace_name from dba_rollback_segs where status='NEEDS RECOVERY';

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

4)Mount the database using new pfile.
Startup mount pfile=’fullpath to pfile’

5)Drop the datafiles,
sql>Alter Database datafile ‘&filename’ offline drop;

6)Open the database.
sql>Alter Database Open;

7)Drop the undo segments,

sql>Drop Rollback Segment “_SYSSMU1$”;
……
8)Drop Old undo tablespace.
sql>Drop Tablespace old_tablespace_name Including Contents;

9)Add the new undo tablespace.

10) Shutdown Immediate;

11) Change the pfile parameters back to Undo_management = AUTO and modify the parameter Undo_tablespace=new_undo_tablespace_name and remove the _offline_rollback_segments parameter.

12) Startup the Database.