no space left on device

This seems like it would be a common question, but I didn't find much that helped in a search...

I have a script scheduled in my crontab that outputs to /dev/null

ie: /dir/scripts/script1 > /dev/null

I have recently started getting the error:

cp /dir1/dir2/file.xls: No space left on device

Does this mean there is no space left on /dev/null, or the device I am copying to?
Thanks in advance, I apologize for the basic question, but my lack of hands on experience makes it just out of my reach.
-kristy

Turns out that the filesystem the target directory resides in was at 100% capacity.