High Performance Optical File System

High performance optical file system (HPOFS) is an IBM-developed media format architecture available to use when initializing optical media on the i5/OS™.

i5/OS uses the WORM-based version of HPOFS. This media format is designed (and required) for WORM media, but you can use it (and it is the default) when initializing erasable optical media. HPOFS is a WORM media format. You can write each sector of the media only once when creating and updating files and directories. This unique characteristic of never rewriting the same sector allows all previous versions of every file to remain on the media. One drawback of this is that media consumption continues to grow as you update and even delete files.

This section contains detailed information on the i5/OS implementation of HPOFS for directly-attached optical media libraries. This section does not address HPOFS characteristics for LAN-attached optical media libraries.

Detailed information on the i5/OS implementation of HPOFS for directly attached optical media libraries is available in the CL command support for media formats.

• Volume, directory, and file names for HPOFS
  HPOFS volume identifiers can be a maximum of 32 characters and must contain only alphabetic characters (A through Z), numeric characters (0 through 9), a hyphen (-), or a period (.).
• Space reclaim
  You can update or delete files even though HPOFS is a write-once read-many (WORM) media format.
• Programming interfaces (HPOFS)
  You can create or read files on HPOFS media by using either the Hierarchical File System (HFS) application programming interface (API) or the integrated file system application programming interface (API).
• Directory structure and performance (HPOFS)
  HPOFS volumes have a dual directory structure to access files. Both a hash and hierarchical structure exist to provide a primary and secondary path to the file data. If the primary directory structure becomes damaged, the secondary path is used.
• Media interchange between LAN and direct attach libraries
  This topic lists how HPOFS formatted optical media created in a LAN-attached optical library can be accessed.