Optical storage

Use the information that is described as an overview and reference guide for IBM® optical support to a system with the IBM i operating system. Optical storage is any storage method that uses a laser to store and retrieve data from optical media.

Start of changeExamples of this media are compact disk read-only memory (CD-ROM), digital versatile disk read-only memory (DVD-ROM), digital versatile disk random access memory (DVD-RAM), write-once read-many (WORM) cartridges, erasable optical cartridges, and Removable Mass Storage (RMS) media which are removable disk (RDX) and flash drives.End of change

These functions are unique to optical support:
  • CD-ROM devices
  • DVD devices
  • Directly attached optical media library devices
  • LAN-attached optical media library devices
  • Virtual optical devices
  • Start of changeRDXEnd of change
  • Start of changeFlash drivesEnd of change

Start of changeRMS devices and media are considered optical storage class for the purposes of supporting commands and functions on IBM i. All references to DVD devices and media in the optical storage section can be considered to also include RMS devices and media. For more information about RMS media and devices, see Removable Mass Storage (RMS).End of change

This information is intended for the following users:
  • System operators and users can use this information as their primary reference for CD-ROM, DVD, optical media libraries, and virtual optical support.
  • Service representatives can use this information to perform activities as directed by the appropriate optical device service guides.

Optical storage on the system provides an economical and efficient way to store and retrieve large amounts of information at a high performance level. Optical storage devices offer significant advantages over other high-capacity storages devices, such as tape and microfilm, with faster access times and a hierarchical-type file organization. IBM i optical storage uses files that are stored in directories and files that are stored in subdirectories similar to UNIX or PC-based file systems.

The capacity, price, and performance of optical storage continually improve, and IBM remains committed to providing its customers with these improvements over time. Even as new devices are introduced, the basic methods of accessing optical information remain consistent, as these new storage devices are being added under the current file system interfaces that optical storage programs have used for years.

These are some considerations in the use of optical storage media:
Consideration Reason for use
Durability Optical media can have a shelf life in excess of 50 years.
Archive storage Write-once read-many (WORM) optical media can be used to archive large amounts of data. Each sector on the media is only written once when creating and updating files and directories. When a file is changed or deleted, a new version of the file gets written, but the old version still exists on the media. All previous versions of the file remain recorded on the media. This capability also exists on erasable media, but the entire disk can be erased and reused.
Transportability Universal Disk Format (UDF) optical media can be read with any other industry operating system platform that supports UDF, which is an industry standard file system. Optical Media written with High Performance Optical File System (HPOFS) format can be interchanged with other optical media libraries attached to a system.
Random access Optical devices are random access devices. This facilitates the retrieval of relevant data on demand. File access is independent of the order in which the data was stored. Also, multiple users can access the same volume at the same time.

Start of changeWhen you use virtual optical storage, you create and use optical images that are stored on your disk units. These optical images are treated as if they were real optical disk media by the internal file system functions. The term virtual applies to the emulation of the optical media sectors when used by read and write functions. End of change