keeping the BAT open (I always use "bat("name").XXX", or keep a ref variable in a block. So, as far as I can tell, I should not have 7500 BATs open at once. Am I misunderstanding? Or is there some underlying component/module keeping the BATs open? Or is this just the amount of memory MonetDB will use? I do not have a BAT of BATs (as I was sure that this would cause problems, and from your description, will indeed). Thanks! Ed