directory-spec

    Name of the directory containing the loadable images of the
    executive. This parameter defaults to SDA$READ_DIR, which is a
    search list of SYS$LOADABLE_IMAGES, SYS$LIBRARY, and SYS$SYSTEM.

 filespec

    Name of the device, directory, and file from which you want to
    read global symbols. The filespec defaults to SYS$DISK:[default-
    dir]filename.type, where SYS$DISK and [default-dir] represent
    the disk and directory specified in your last DCL command SET
    DEFAULT. If no type has been given in filespec, SDA first tries
    .STB and then .EXE.

    If no device or directory is given in the file specification, and
    the file specification is not found in SYS$DISK:[default_dir],
    then SDA attempts to open the file SDA$READ_DIR:filename.type. If
    no type has been given in filespec, SDA first tries .STB and then
    .EXE.

    If the file name is the same as that of an execlet or image, but
    the symbols in the file are not those of the execlet or image,
    then you must use the /FORCE qualifier, and optionally /RELOCATE
    and /SYMVA qualifiers, to tell SDA how to interpret the symbols
    in the file.

    The READ command accepts quoted filenames for access to images on
    ODS-5 disks with lowercase or compound characters in their names.