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ODS-2, or On-Disk Structure-2, is a Files-11 file system. This is the most widely used file system on OpenVMS; system disks can only be ODS-2. The most notable feature of this system as compared to the other most widely used one, ODS-5, is that it is not case-sensitive or case-preserving, and that it does not support hard links.

ODS-2 is used to share data between VAX and Alpha with full compatibility.

Here is what an ODS-2 disk looks like:

$ sh dev dka0: /full

Disk SMAN01$DKA0:, device type RZ73, is online, mounted, file-oriented device,
    shareable, available to cluster, error logging is enabled.

    Error count                    0    Operations completed               8514
    Owner process                 ""    Owner UIC                      [SYSTEM]
    Owner process ID        00000000    Dev Prot            S:RWPL,O:RWPL,G:R,W
    Reference count               94    Default buffer size                 512
    Total blocks             3907911    Sectors per track                     7

  Volume Status:  ODS-2, subject to mount verification, protected subsystems
      enabled, file high-water marking, write-through XFC caching enabled,
      write-through XQP caching enabled.

File Name Restrictions

ODS-2 supports the following character set:

  • A-Z
  • 9-0
  • hyphen (-)
  • dollar sign ($)
  • underscore (_)

The maximum length of file names and extensions is 39 characters.

See also