Manage virtual files
Since version 3.2 of the Nextcloud sync client the feature "virtual files" was introduced on Windows clients and later even was made the default setting for fresh installations.
In short, in this mode the sync behavior is different, as the files are only synced on access and not beforehand. In case of a maintenance or if you are just offline, you will not be able to access your files. On the other hand, you save local disk space for files you do not use, so there is no definite answer on which mode is the best for you. For mobile computers, or computers that are expected to be offline frequently, we recommend to deactivate the virtual files feature and always have a local copy of your files.
Find out your sync-mode
There are multiple ways to find out the mode that your Nextcloud sync client operates. One is the Windows Explorer. For virtual files the sync status is shown in a separate column in the list view.
The cloud-symbol is meant to show files that are not accessible offline, but are only stored in the cloud. The files will be automatically downloaded on access.
Another way to check the sync mode is the settings dialog of the Nextcloud sync client. You can open the settings dialog by a right click on the Taskbar icon of the Nextcloud application and then choose Settings. In the settings window you will find the text "Synchronize VirtualFiles with local folder" next to the big green checkmark icon.
Activate virtual files
In order to activate the virtual files feature, open the settings dialog of the Nextcloud sync client. You can open the settings dialog by a right click on the Taskbar icon of the Nextcloud application and then choose Settings. Click in the ...-Button to open a context menu and choose Enable virtual file support. The process will start immediately and all local copies will be removed and replaced by placeholder files.
If this mode is active, the Nextcloud client will manage to download files on access as well as to clear unused files from the local disk again. You can trigger both directions by hand, as seen is the next paragraph.
Force sync of selected folders
You can choose to force selected files or folders to be always synced to your machine. Therefore, open the Windows Explorer and do a right click on the file or folder, then from the context menu choose Nextcloud > Make always available locally. Of course, changes to these local copies will always be synced to the CAU-Cloud as you would expect. To revert this permanent sync, you have to free up the space once manually, as seen in the next paragraph. Then the availability will be managed automatically again.
Free up local disk space
If you want to manually free up disk space or revert the file or folder to be always synced to the automatically managed state, you can do this just like describes in the force sync paragraph but then choose "Free up local space" from the context menu. Here we will see a different way to manipulate the sync state for folders in the settings dialog of the Nextcloud Client.
You can open the settings dialog by a right click on the Taskbar icon of the Nextcloud application and then choose Settings. In the folder tree you can right click a folder and then choose "Availability > Free up local space".
Deactivate the virtual files feature
Do deactivate the virtual files feature, open the settings dialog of the Nextcloud sync client. You can open the settings dialog by a right click on the Taskbar icon of the Nextcloud application and then choose Settings. Click in the ...-Button to open a context menu and choose Disable virtual file support. A dialog window will open and inform you that all files and folders will be downloaded to your computer and you have to acknowledge this with the button Disable support.
Now the client will start to sync all your files and folders from the CAU-Cloud. Dependent of the number and size of files, this can take a while.