That’s how to change the Oracle Database’s TEMP and UNDO tablespaces to bigfile (as possible in 10g and above). It’s something I usually do for every DB I install.
create bigfile temporary tablespace TEMP1 tempfile \
size 10G autoextend on next 1G maxsize 20G;
create bigfile undo tablespace UNDO1 datafile \
size 10G autoextend on next 1G maxsize 20G;
alter system set undo_tablespace=UNDO1 scope=both sid='*';
alter database default temporary tablespace TEMP1;
drop tablespace UNDOTBS1;
drop tablespace TEMP;
Be careful,
Usn