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.

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