Memory Mapping on a Virtual Machine

Question

I have an application that memory maps a number of files. Occasionally it needs to unmap them so that they can be updated. On a real machine this process works flawlessly but I have two installs that are on virtual machines. On the virtual machine installs the unmapping occasionally seems to either fail or at least take a long time. When I come to update the file I get the "The requested operation cannot be performed on a file with a user-mapped section open" error message.
The failure is fairly random, sometimes the update process works sometimes is fails and it doesn't consistently fail on the same mapped file which is why I think it's something to do with the timing of the unmapping and the virtual machine environment. Both virtual machine installs are running on Windows 2003 Server.
Has anyone else seen this? I'm going to try inserting a pause between the unmapping and the update but that feels like a hack, I'd rather a call back to tell me the unmapping is complete but I don't suppose that's possible.

Answer 1

the_doozer wrote:
Ok, I'll grant you there is no way to explicitly unmap a mapped file in Java (a huge failing of the file mapping system IMHO) but closing any open FileChannel and nulling out the MappedByteBuffer is, in my experience, normally enough to cause the OS to unmap the file. This system lets me update files quite happily on all but the virtual machine system.I think you've been lucky in that case. I had some test cases that consistently failed since I couldn't delete the memory mapped file that I previously had created.