Applications that do not support the new ODS-5 volume structure do not operate successfully on these volumes even if they encounter only traditional file specifications. These applications use physical or logical I/O to bypass the file system when they access the volume or access directory files or other metadata files directly, and therefore must be installed with privileges or run by a user who has privileges. These applications are usually system programs, such as disk defragmenters, or programs that try to avoid overhead by accessing the disk directly. These applications rely on specific knowledge of the file or directory structure on the disk which has changed with introduction of the ODS-5 structure. Recommendations: Applications should use documented interfaces and structures whenever possible.