procedure form_file(p_date in date default trunc(sysdate-1)) as
  l_clob clob;
  f_blob blob;
  l_id number;
  line varchar2(32767);
  s_offset pls_integer := 1;
  d_offset pls_integer := 1;
  def_lang_context pls_integer := dbms_lob.DEFAULT_LANG_CTX;
  wrn pls_integer;
begin
  dbms_lob.createtemporary(l_clob, true);
  
  line := 'Некоторый русский текст';
  line := convert(line, 'CL8MSWIN1251');
  
  dbms_lob.writeappend(lob_loc => l_clob,
                       amount => lengthc(line),
                       buffer => line
                      );
  
  for rec in (select some_string
                from some_table
              )
    loop
      line := some_string;
      line := convert(line, 'CL8MSWIN1251');
      dbms_lob.writeappend(lob_loc => l_clob,
                           amount => lengthc(line),
                           buffer => line
                          );
    end loop;
  
  insert into ra_upload_files(file_name, mimetype, up_file, filecharset, file_date, description) 
    values('Report.csv', 'text/plain', empty_blob(), 'CL8MSWIN1251', sysdate, 'TEST.') 
    returning id, up_file into l_id, f_blob;
  dbms_lob.open(f_blob, dbms_lob.lob_readwrite);   
  
  begin
    dbms_lob.converttoblob(dest_lob => f_blob,
                           src_clob => l_clob,
                           amount => dbms_lob.getlength(l_clob),
                           dest_offset => d_offset,
                           src_offset => s_offset, 
                           blob_csid => dbms_lob.DEFAULT_CSID,
                           lang_context => def_lang_context,
                           warning => wrn);
    dbms_lob.close(f_blob);
    commit;
  exception when others then dbms_lob.close(f_blob);
                             raise;
  end;

  dbms_lob.freetemporary(l_clob);
end form_file;

convert(line, 'CL8MSWIN1251', 'AL32UTF8');

SELECT NLS_CHARSET_ID('CL8MSWIN1251') into csid FROM DUAL; 
dbms_lob.converttoblob(dest_lob => f_blob,
                           src_clob => l_clob,
                           amount => dbms_lob.getlength(l_clob),
                           dest_offset => d_offset,
                           src_offset => s_offset, 
                           blob_csid => csid,
                           lang_context => def_lang_context,
                           warning => wrn);