To clear out all the events in the database, go to Settings > Tools > Clear Events. The Clear Events page allows you to delete all alerts, plus application and page events in Skope IT.
If you click Delete All Events, all event information is permanently deleted and you cannot get it back. Event information on the Devices page is permanently deleted as well.
You can also clear the query service cache which stores data used in reports. After clicking Delete Query Service Cache, reports will be slower as there will be no cached data. However, the cache will get replenished as the report subsequently runs.