Causes for main memory to be unloaded - BIA Server is overloaded

The check on our BIA server is showing "BIA Server is overloaded".

The details indicate that the main memory was unloaded >900 times in the last 24 hours.

I am not aware of any special activities taking place - what would be the cause of the main memory being unloaded so frequently?

The indices only take up 25% of main memory, which is well below the 50% threshold recommended by SAP.

What else might be the cause?

Thanks