Editing Files-11 (section)

== Overview ==
"Files-11" is the general term for five separate file systems, known as on-disk structure (ODS) levels 1 through 5.

'''ODS-1''' is the [[flat file system]] used by the RSX-11 OS, supported by older [[OpenVMS|VMS]] systems for RSX compatibility, but never used to support VMS itself; it has been largely superseded by ODS-2 and ODS-5.

'''ODS-2''' is the original VMS file system. Compared with ODS-1, it is a [[hierarchical file system]].

Although seldom referred to by their ODS level designations, '''ODS-3''' and '''ODS-4''' are the Files-11 support for the CD-ROM [[ISO 9660]] and [[High Sierra Format]] file systems, respectively.

'''ODS-5''' is an extended version of ODS-2 available on [[DEC Alpha|Alpha]], [[IA-64]] and [[x86-64]] platforms which adds support for [[case-preserving]] filenames with non-[[ASCII]] characters and improvements to the hierarchical directory support. It was originally intended for file serving to [[Microsoft Windows]] or other non-VMS systems as part of the "NT Affinity" project, but is also used on user disks and [[Internet]] servers.