ORA-01552: cannot use system rollback segment

Hi all,

When I tried to open my secondary mounted database, ORA-01552 was thrown. Did a bit of google for this error and it was successfully resolved through the below simple steps.

*** Firstly all the rollback segements were checked.

select segment_name,tablespace_name,status from dba_rollback_segs;

*** Brought the UNDO tablespace online.

alter database datafile ‘/home/app/host/undotbs01.dbf’ online;

*** Set the undo management to AUTO. You will need to restart the DB.

alter system set undo_management=AUTO scope=spfile;

*** Brough the rollback segments to online.
ALTER ROLLBACK SEGMENT “_SYSSMU1_99961370$” online;