Drop Undo Tablespace

After switch from UNDO Tablespace UNDOTBS1 to UNDOTBS2, UNDOTBS2 Tablespace is still exists.

Need to drop it manually.

After dropping UNDOTBS2, database cannot be started

WTF...

Steps and how to fix

COL TABLESPACE_NAME FOR A30

COL STATUS FOR A20

SELECT tablespace_name, status, count(*) 

FROM DBA_ROLLBACK_SEGS 

GROUP BY tablespace_name, status;

TABLESPACE_NAME           STATUS                 COUNT(*)

------------------------- -------------------- ----------

UNDOTBS1                  ONLINE                       41

SYSTEM                    ONLINE                        1

UNDOTBS2                  OFFLINE                       0

In detail:

SET LINESIZE 160

SELECT owner, segment_name, tablespace_name, status 

FROM DBA_ROLLBACK_SEGS ORDER BY 3;

SYS    SYSTEM                SYSTEM  ONLINE

PUBLIC _SYSSMU42_3536664823$ UNDOTBS ONLINE

PUBLIC _SYSSMU43_1783674736$ UNDOTBS ONLINE

PUBLIC _SYSSMU44_629285899$  UNDOTBS ONLINE

PUBLIC _SYSSMU45_2404285950$ UNDOTBS ONLINE

PUBLIC _SYSSMU46_132405334$  UNDOTBS ONLINE

DROP TABLESPACE UNDOTBS2 INCLUDING CONTENTS AND DATAFILES;

At this point oracle crashed and could no be started.

Upon startup, this error is coming:

ORA-00603: ORACLE server session terminated by fatal error
ORA-01092: ORACLE instance terminated. Disconnection forced
ORA-30012: undo tablespace 'UNDOTBS2' does not exist or of wrong type
Incident details in: /software/oracle/diag/rdbms/igt/igt/incident/incdir_2131503

How to fix

Option 1. The proper solution:

CREATE PFILE FROM SPFILE

Edit PFILE so that oracle is aware of the correct tablespace

Start oracle from PFILE

Option 2. The quick solution:

make a copy from spfile

edit the binary file spfile

Replace from 

*.undo_tablespace='UNDOTBS2'

to 

*.undo_tablespace='UNDOTBS1'

Start oracle

Now it starts without an error