How to clear locally cached OneDrive online-only files

I recently needed to free up some space on my Dell Venue 8 Pro, running Windows 8.1, and realized that I had OneDrive set for all files to be available offline, meaning it was caching local copies of all files. No problem, I thought. I'll just change it globally to make the files available as online-only. I've read that the files then do not consume space locally. Instead, there are place holder shortcuts which allow browsing of the file structure, and files are only downloaded when accessed or marked to be available offline.

However, after changing the global OneDrive setting for all files to be online-only, the local files continue to consume their full space (13 GB). I cannot delete the files as they are then deleted in the cloud. I would have expected that after marking all the files as online-only, the bits would start deleting, or perhaps after some definable period of time of not being accessed. Or at least have a button to manually flush the local OneDrive file cache. Alas, 'tis not so. How can I clear the local OneDrive file cache for online only files?

If you have set your files to online-only, you are probably being tricked by the new and wonderful cloud integration of Windows 8.

From the Microsoft article Online-only files and files available offline :

Online-only files, also called smart files, are a special kind of OneDrive file in Windows 8.1 and Windows RT 8.1. You can browse them on your PC, but the file contents are really in OneDrive, so they don’t take up much of your disk space. Online-only files look like normal files on your PC, they have all the typical file info (like date modified, file type, and size), and you can search them. When you open online-only files from File Explorer and most apps, the file contents are downloaded automatically.

This wonderful transparency assumes that one has continuous Internet connectivity. Imagine getting on a plane and suddenly discovering that those files thought to be on the PC are, in fact, not there. Only the "smart" placeholders are there, and stupidly enough can't be opened while offline.

In my book, this new system is utterly and absolutely broken and user-unfriendly. Until it is fixed, you might be better off using another free online service which is not as well integrated into Windows.