How to clear alerts in enterprise manager (database control)

When alert appear in enterprise manager and with some action solve, it may stay in enterprise manager as shown picture:

Here I'll show you how to clear this unnecessary information.
login into database with sysman user and execute this script:

SELECT t.target_name,
       t.target_type,
       collection_timestamp,
       MESSAGE,
          'exec em_severity.delete_current_severity('''
       || t.target_guid
       || ''','''
       || metric_guid
       || ''','''
       || key_value
       || ''')'
          em_severity
  FROM    sysman.mgmt_targets t
       INNER JOIN
          sysman.mgmt_current_severity s
       ON t.target_guid = s.target_guid;

result:

after that run this scripts

SQL> exec em_severity.delete_current_severity('C894D538793FFA3B4727BCBCD84D4925',
'3F2BBE6BF105C0D16A3710F2868B8399','RECOVERY AREA');

PL/SQL procedure successfully completed.

SQL> commit;

Commit complete.

same way you can clear entire alerts.