Normally an event created as the result of an alarm consists of entries in one or more database tables plus the various files associated with it. When deleting events in the browser it can take a long time to remove all of this if your are trying to do a lot of events at once. It is recommended that you set this option which means that the browser client only deletes the key entries in the events table, which means the events will no longer appear in the listing, and leaves the zmaudit daemon to clear up the rest later.