knime will not release memory

when I close a workflow, the memory is not released. I have to close knime completely to release. Is there a way to control or change this?

Hi clac2188, 

Please activate the heap status bar shown when you select "File" -> "Preferences" -> "General" -> "Show Heap Status" and run the garbage collector (press the trash bin icon in the heap status bar at the bottom of the KNIME window).