VMS Help ASSIGN, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 equivalence-name[,...]

    Specifies a character string of 1 to 255 characters. Defines the
    equivalence name, usually a file specification, device name, or
    other logical name, to be associated with the logical name in
    the specified logical name table. If the string contains other
    than uppercase alphanumeric, dollar sign ($),  or underscore (_)
    characters, enclose it in quotation marks (" ").  Use two sets
    of quotation marks ("" "")  to denote an actual quotation mark
    within the string. Specifying more than one equivalence name for
    a logical name creates a search list.

    When you specify an equivalence name that will be used as a file
    specification, you must include the punctuation marks (colons
    (:),  brackets ([]),  and periods (.)) that would be required if
    the equivalence name were used directly as a file specification.
    Therefore, if you specify a device name as an equivalence name,
    terminate the device name with a colon.

    The ASSIGN command allows you to assign the same logical name to
    more than one equivalence name. When you specify more than one
    equivalence name for a logical name, you create a search list.
    For more information on search lists, refer to the OpenVMS User's
    Manual.

 logical-name[:]

    Specifies the logical name string, which is a character string
    containing up to 255 characters. You choose a logical name to
    represent the equivalence name in the specified logical name
    table.

    If the string contains other than uppercase alphanumeric, dollar
    sign, or underscore characters, enclose it in quotation marks.
    Use two sets of quotation marks to denote an actual quotation
    mark. If you terminate the logical-name parameter with a colon,
    the system removes the colon before placing the name in a logical
    name table. (This differs from the DEFINE command, which saves
    the colon.) If the logical name is to be entered into the
    process directory (LNM$PROCESS_DIRECTORY) or system directory
    (LNM$SYSTEM_DIRECTORY) logical name tables, then the name may
    only have from 1 to 31 alphanumeric characters (including the
    dollar sign and underscore). By default, the logical name is
    placed in the process logical name table.

    If the logical name contains any characters other than
    alphanumeric characters, the dollar sign, or the underscore,
    enclose the name in quotation marks. If the logical name contains
    quotation marks, enclose the name in quotation marks and use
    two sets of quotation marks in the places where you want one set
    of quotation marks to occur. Note that if you enclose a name in
    quotation marks, the case of alphabetic characters is preserved.