You must use an operating system utility to back up the AI files regardless of whether you are using a single AI file or multiple AI files. Ensure that the backup technique backs up the entire file. On many UNIX systems, certain utilities (for example, cpio) will back up only the first part of files over a certain size (controlled by the ULIMIT parameter). Backups of partial AI files are invalid and unusable. If you use ftp to transfer the AI files to a different machine, binary mode must be used. Failing to use ftp in binary will leave your AI files in an unusable state.