Some example are :
- undo tablespace was dropped
- undo was not recreated
- undo was recreated without specifying 'undo' keyword.
To resolve the issue, Follow the following steps :
- set undo_management to MANUAL
- startup pfile
- drop undo tablespace (If it was created wrongly without undo keyword)
- create undo tablespace undotbs datafile '??????' size 1M reuse;
- shutdown database.
- set undo_management to AUTO-