Stub file

A stub file is a computer file that appears to the user to be on disk and immediately available for use, but is actually held either in part or entirely on a different storage medium. When a stub file is accessed, device driver software intercepts the access, retrieves the data from its actual location and writes it to the file, then allows the user's access to proceed. Typically, users are unaware that the file's data is stored on a different medium, though they may experience a slight delay when accessing such a file.