File handles of mounted objects (directories or file systems) are saved on DASD in a mount handle data set and are automatically established again when the server restarts. However, file handles for the files within a mounted object are kept in virtual storage (memory) and they are lost if the server restarts. This may result in stale file handles for NFS version 2 and 3, or file handle expired in NFS version 4, and the clients may be required to request a new file handle by redoing the lookup on the file.