/READ_ONLY
       /NOREAD_ONLY

    Specifies whether or not the buffer you create is read-only and
    therefore unmodifiable. This qualifier and the /WRITE qualifier
    override any setting established by the SET DIRECTORY command. The
    /WRITE qualifier is equivalent to the /NOREAD_ONLY qualifier.

    If you specify neither the /READ_ONLY nor the /WRITE qualifier,
    LSE uses the default established by the most recent SET DIRECTORY
    command for the directory that contains the file. If during your
    current editing session you have not issued a SET DIRECTORY
    command nor defined the logical LSE$READ_ONLY_DIRECTORY, then
    the buffer is writeable by default.