Perhaps you have been receiving alerts/alarms after you have deleted mnemonics. This might seem like strange behaviour and you are not sure why. 

The alarms you received were not new alarms but rather reminder notifications that get sent every six hours if an event/alarm has not been acknowledged in the events manager.

The system will still display the events for between 24 and 48 hours before they are aged out of the system entirely. To prevent alarm notifications to be sent, the alarms should be deferred or acknowledged.