Using RoboCopy with Dropbox “Online Only” Files
The Dropbox Smart Sync feature allows files or folders to appear in the user's Dropbox folder but not consume any local storage. When the user opens the file, the Dropbox client downloads it, and then the file opens as normal.
Smart Sync is a way to manage large Dropbox archives on smaller drives, because the user does not necessarily need all the files available locally all the time. OneDrive has similar functionality.
One issue with this is that if the folder is included in a copy operation, the copy process attempts to read each file, which triggers the Dropbox/OneDrive client to download the file. This can consume significant internet usage and local storage.
To avoid this, use the RoboCopy command with /xa:o. This causes the operation to skip files with the “Offline” attribute set.