The db is at mount state..
shall i do the following?

Create UNDO1 Tablespace undo_tbs1
datafile '/vol1/data/uday/undotbs1.dbf' size 25m autoextend on;
shutdown immediate;;
change undo_tablespace parameter in init.ora to undo1 from undo
startup mount
alter tablespace undo offline drop including contents;

will this work?