Extended File Specifications consists of two main features, the
    ODS-5 volume structure, and support for deep directories.

1  –  ODS-5

    OpenVMS Alpha Version 7.2 and later implements On-Disk Structure
    Level 5 (ODS-5). This structure provides the basis for creating
    and storing files with extended file names. You can choose
    whether or not to enable ODS-5 volumes on your OpenVMS Alpha
    systems.

    The ODS-5 volume structure allows the following features:

    o  Long file names

    o  More characters legal within file names

    o  Preservation of case within file names

2  –  Deep Directories

    Both ODS-2 and ODS-5 volume structures support deep nesting of
    directories, subject to the following limits:

    o  There can be up to 255 levels of directories.

    o  The name of each directory can be up to 236 8-bit or 117
       16-bit characters long.

    Complete file specifications longer than 255 bytes are
    abbreviated by RMS when presented to unmodified applications.

    For example, a user can create the following deeply nested
    directory:

    $ CREATE/DIRECTORY [.a.b.c.d.e.f.g.h.i.j.k.l.m]

    A user can create the following directory with a long name on an
    ODS-5 volume:

    $ CREATE/DIRECTORY
    [.AVeryLongDirectoryNameWhichHasNothingToDoWithAnythingInParticular]

2.1  –  Directory Naming Syntax

    On an ODS-5 volume, directory names conform to most of the same
    conventions as file names when using the ISO Latin-1 character
    set. Periods and special characters can be present in the
    directory name, but in some cases, they must be preceded by a
    circumflex (^) in order to be recognized as literal characters.