Go to > Administration > Options > Alarm > Advanced
Here you'd set the parameters for the Action Queue.
Click on help and read about the function - in my opinion that would mean that you generate alarms (and linked actions) faster then EMC could empty the Q which either means you've a huge networks with a lot of alarms/actions or there is a problem.
I don't see a option to clear the Q - and in my opinon that wouldn't make sense as it would remove actions.