I ran into a small problem with using ownCloud after manually copying 300GB of data from a usb drive my ownCloud was not seeing the file, I did a lot of looking around for a solution to this and found that there are some plugins to rescan but none of this seemed to work with version 6.
What I did find is that it already has a built in feature re scanning files.
On my Linux box (CentOS 6) I logged in via ssh, went to my owncloud root folder updated the occ file to have execute permissions
chmod +x occ
then I ran the file with the argument files:scan –all
./occ files:scan --all
this then proceeded to rescan all files which then started to show in the web interface.
Hope this helps you as much as it did me, uploading large volumes of data to ownCloud is fine if you are on the same network but not so great over the internet.