You cannot start a database without undo space. You have to choose between the MANUEL and AUTOMATIC mode management. It is recommand to run in automatic mode. To configure the auto mode, follows the steps below:
1) Create an undo tablespace:
<b>CREATE UNDO TABLESPACE undotbs_01
DATAFILE ‘path_of_the_file_.dbf’ SIZE 2M REUSE AUTOEXTEND ON;</b>
2) In your parameter file add the lines bellow
– UNDO_TABLESPACE= undotbs_01</b>
After perfoms steps 1 and 2, start your database. Now it is running in auto undo management mode.
You can execute the following command at the prompt of sqlplus to see the mode and the tablespace of undo: <b>Show parameter undo;</b>