Scheduled to be copied next time the system starts

During a sync process all of a sudden DO shows this pop-up window

"Please note that one or more files have been scheduled to be copied next time the system starts.
You should restart your computer now if you would like these files copied immediately."
Only 1 button "OK"

Never seen this weird pop-up.

Why is this ?

a minute later:
I clicked ok and cannot launch Directory Opus anymore.
whatever I try.

Guess I solved it myself, had to kill Dopus.exe from the tasklist first - then I could lauch DO again.
Still the above puzzles me...

You see that message if a file was in use an couldn't be copied over, and you then selected the Schedule option when prompted. At least, that's the only time I can think of where it would happen.

The purpose of the Schedule option is to allow you to replace program or OS files which can only be copied over during a reboot.

As for why Opus stopped working, were any of the files you were modifying part of Opus or OS components which Opus might have been using?

I was synchronizing two folders containing non-installed applications only, i.e. apps that should be double-clicked in order to be setup (like DOpusinstall64.exe). Source folder to backup folder. So nothing was 'in use' or being modified, I guess.
Strange error.

I found it,2 small files of 8kb were in use indeed. The sync did not skip the files but got me this unfamiliar pop-up.