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

    Enables error checking by the command interpreter after the
    execution of each command in a command procedure. Specify SET
    NOON to disable error checking.

    Format

      SET [NO]ON

1 - Example

  $ SET NOON
  $ DELETE  *.SAV;*
  $ SET ON
  $ COPY  *.OBJ  *.SAV

      This command procedure routinely copies all object modules
      into new files with the file type .SAV. The DELETE command
      first deletes all existing files with the .SAV file type, if
      any. The SET NOON command ensures that the procedure continues
      executing even if there are no files with the .SAV file type
      in the current directory. Following the DELETE command, the SET
      ON command restores error checking. Then the COPY command makes
      copies of all existing files with .OBJ file type.