VMS Help DSR, DSR Commands, .SPACING, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 n

    The amount of spacing that you want between lines of text. For
    example, 1 denotes single spacing (no blank lines between lines
    of text). You must specify n, which must be within the range of 1
    to 5, inclusively.