Currently, the size limit is 4096 0bjects. Since the largest object is an 8byte double, the max # bytes is 8*4096. Russ and I discussed this prefetch issue a long time ago. I will ask him if he remembers why we chose prefetch as the default. I think it was a performance issue. But I must re-iterate: I think using presence of a constraint as a means to limit data access is a bad idea. You should get the grads server developers to implement size based limit. =Dennis Heimbigner Unidata Ticket Details =================== Ticket ID: TMR-458993 Department: Support netCDF Priority: Urgent Status: Closed