/sys$common/syshlp/helplib.hlb CMS, RESERVE, Command Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 element-expression

    Specifies the element or elements from which a generation is
    to be reserved. An element expression can be an element name,
    a group name, a wildcard expression, or a list of these separated
    by commas. By default, CMS reserves the most recent generation
    on the main line of descent of each element designated by the
    element-expression.

 remark

    Specifies a character string to be associated with the reservation
    and logged in the history file with this command. The remark is
    enclosed in quotation marks. If no remark was entered, a null
    remark ("") is logged.