The cio (Concurrent I/O) option specifies the file system to be mounted for concurrent reads and writes. Concurrent I/O is a licensed feature of VxFS. If cio is specified, but the license is not present, the mount command prints an error message and terminates the operation without mounting the file system. The cio option cannot be disabled through a remount. To disable the cio option, the file system must be unmounted and mounted again without the cio option.