Universal disk format

 

Universal Disk Format (UDF) is the Optical Storage Technology Association (OSTA) 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 reclamation capabilities as well as file and directory-level security. This section contains detailed information on the implementation of UDF for directly attached (C4x) 3995 optical media libraries as well as for a DVD-RAM device.

Although not accessible through i5/OS® operating system, CD and DVD media that are created using the supplementary volume descriptor of ISO 9660 may be accessible in a system. You can access them through an integrated system. For more information, see the Windows® environment on System i™ 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 Universal Disk Format (UDF) media by using either the Hierarchical File System (HFS) application programming interface (API) or the integrated file system API. There are things specific to the i5/OS implementation of the UDF that application developers need to know.
  • Directory and file security
    Directory- and file-level security is available for Universal Disk Format (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
    Universal Disk Format (UDF) media created on the i5/OS operating system is UDF Version 2.01. This media can be interchanged to other operating systems that support this version of UDF.
  • Directory structure and performance (UDF)
    Universal Disk Format (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