Trabnsfer the output into the open dataset

I am trying to get the output of a program into a file . First I was trying to get the output into the P drive but unfortunately it didnt work . I am trying to run the program (upoad program) in background and get the error log which is the output of the program into a file on my P drive. Is it possible to get the file onto the P drive when I run a upload program from a file on the application server in the background?

form write_err_file .

IF v_zss = 1.
  case p_as.
    when 'X'.                      "X is application server
*         TRANSLATE p_err USING '\/'." correct slash for unix
      open dataset p_err for output in text mode encoding default.
      if sy-subrc = 0.
        loop at t_err into s_dls.
          transfer s_dls to p_err.
          if sy-subrc ne 0.
            message i010(ad) with p_err 'Download Failed'.
          endif.
        endloop.
        close dataset p_err.
      else.
*            message i010(ad) with p_err 'dataset could not be found'.
        sy-subrc = -1.             "Maintain error condition
      endif.
    when ' '.                      "Blank is presenation server
      translate p_err using '/\'."correct slash Dos file
      call function 'DOWNLOAD'
        EXPORTING
          filename = p_err
          filetype = 'ASC'   "FTYPE set to DAT in DATA seg
        TABLES
          data_tab = t_err.
      if sy-subrc ne 0.
        message i010(ad) with 'File ' p_err 'cannot be located.'.
        sy-subrc = -1.             "Maintain error condition
        exit.
      endif.
  endcase.

 ELSE.

This si not letting teh file in my P drive to be updated or written.

Thanks