ORA-29283：无效的文件操作ORA-06512：在“ SYS.UTL_FILE”的第536行处

BEGIN
    DECLARE
        file_name VARCHAR2(50);
        file_handle utl_file.file_type;
BEGIN
    file_name := \'table.txt\';
    file_handle := utl_file.fopen(\'SEND\',file_name,\'W\');
FOR rec in(
    SELECT            column 1
                ||\'~\'||column 2
                ||\'~\'||column 3 out_line
    FROM table1)LOOP
UTL_FILE.PUT_LINE(file_handle,rec.out_line);
UTL_FILE.FFLUSH(file_handle);
END LOOP;
UTL_FILE.FCLOSE(file_handle);
END;
end;

Error starting at line 1 in command:
    BEGIN
    DECLARE
        file_name VARCHAR2(50);
        file_handle utl_file.file_type;
BEGIN
    file_name := \'table.txt\';
    file_handle := utl_file.fopen(\'SEND\',file_name,\'W\');
FOR rec in(
    SELECT            column 1
                ||\'~\'||column 2
                ||\'~\'||column 3 out_line
    FROM table1)LOOP
UTL_FILE.PUT_LINE(file_handle,rec.out_line);
UTL_FILE.FFLUSH(file_handle);
END LOOP;
UTL_FILE.FCLOSE(file_handle);
END;
end;

Error report:
ORA-29283: invalid file operation
ORA-06512: at \"SYS.UTL_FILE\", line 536
ORA-29283: invalid file operation
ORA-06512: at line 7
29283. 00000 -  \"invalid file operation\"
*Cause:    An attempt was made to read from a file or directory that does
           not exist, or file or directory access was denied by the
           operating system.
*Action:   Verify file and directory access privileges on the file system,
           and if reading, verify that the file exists.

Oracle directory \'SEND\' points to some UNIX directory which has rights as 
       \'rwxrwsr-x\' (Octal 2775)
Oracle Version:11g