Hi,
your questions seems better to be a LabVIEW application issue so I would please you to set your post in the LabVIEW forum next time.
When you Dequeue an element it will be removed of your FIFO. One should consider that the application architecture is able to dequeue elements faster than they were enqueued. A Queue is a FIFO that holds all enqueued elemts until they were dequeued and therefore it's possible to fill up your memory with elements.
It's possible to check the Queue size during runtime so your application can decide wheather you want to enqueue more elements or first dequeue them. For that the function "Queue status" is very helpful.
On the other side it's also possible to limit the maximum queue size on initialization so the maximum memory used for this queue is also limited.
Hope that helps for further coming along with your application,
regards,
Nikolai