Yonatan is correct, the LabVIEW RT OS, and I believe most if not all RT OS's, do not support virtual memory. The simplified reason is that virtual memory is created through the use of hard drive space which is substantially slower than RAM. Because of the speed difference, you can easily lose the determinism that RT OS's require. The problem is that when you run out of memory on an RT OS, you can get unexpected results as data in memory gets overwritten by incorrect data, or commands fail to allocate memory. In my experience, this most frequently results in the OS crashing with a GPF type fault.
Regards, Aaron Gelfand Certified LabVIEW Developer AMG Design-Consulting