Universal disk format

UDF (Universal Disk Format) is the OSTA (Optical Storage Technology Association) supported subset of ISO/IEC 13346.

UDF also addresses ECMA-167 which is equivalent to ISO 13346. UDF is a writable file format that provides true space reclaim capabilities as well as file and directory level security. This section contains detailed information on the i5/OS™ implementation of UDF for direct-attached (C4x) 3995 optical media libraries as well as a DVD-RAM device.

Note: Although not accessible through i5/OS, CD and DVD media that are created using the supplementary volume descriptor of ISO 9660 may be accessible in an iSeries™ server. You can access them through an integrated server. For more information, see the Windows^® environment on iSeries and Linux^® on an Integrated xSeries^® Solution topics.

Volume, directory, and file names
Volume identifiers can be a maximum of 30 characters and must contain only alphabetic characters (A through Z), numeric characters (0 through 9), a hyphen (-), or a period (.). The first character must be alphabetic or numeric, and the identifier cannot contain imbedded blanks.
Programming interfaces UDF
You can create files or read files on UDF media by using either the Hierarchical File System (HFS) application programming interface (API) or the integrated file system programming interface. There are things specific to the i5/OS implementation of the UDF media format that application developers need to know.
Directory and file security
Directory and file-level security is available for UDF volumes. The system maintains the data authorities of optical directories and files for three groups of users; owner, group, and public. Volume level security is also available through authorization lists.
Media interchange
UDF media created on i5/OS is UDF Version 2.01. This media will interchange to other operating system platforms that support this version of UDF.
Directory structure and performance UDF
UDF volumes have a single (hierarchical) directory structure to access files. Because of this hierarchical directory structure, the depth of a directory tree has a direct impact on file performance. For example, if /DIRECTORY1 contains 1000 files and /DIRECTORY2 contains 100 files, file search times for files in /DIRECTORY1, in general, take longer than file searches in /DIRECTORY2. This is because the system performs file searches hierarchically, which may require looking at every entry in the directory.

Parent topic: Optical media formats