Switch undo to new undo tablespace Oracle 9i onwards

Create New Undo Tablespace

create undo tablespace undo_new datafile
'd:\oracle\oradata\test\undodata1.dbf' size 1024m autoextend off maxsize unlimited online;

Issue these command one or more times to force the commited data write in datafiles.

alter system checkpoint;

alter system switch logfile;

alter database archive log current;

Modify the SIDinit.ora file parameter

undo_tablespace=undo_new

Shutdown the database

shutdown immediate;

Check the parameter value

show parameter undo_tablespace

Drop the old undo tablespace and physical datafiles

drop tablespace undo_old including contents and datafiles;