getMemoryUsage in Tibco Hawk rulebase

We have a Hawk rulebase monitoring memory usage on a Tibco BW process. We have it set to alert if memory usage goes above 96%.

It is now telling us that usage has reached 96% but we don't know why this is as there is no discernible increase in the number of ems messages that the process is dealing with.

Any ideas about why this would happen or how we can control it. Do we need to take some remedial action with this process to reduce this usage from 96%??

Any help appreciated...