Duvida Atualização Dados Banco

private static final String _QueryDeGravacao = "insert into realtime values (?,?,?)";
        private static final String _QueryHistory = "insert into history values(?,?,?,?,?)";
        private static final String _QueryBuscaRealtime = "select * from realtime";
        private static final String _QueryDeletarRealtime = "delete from realtime where PointTag = ?" ;
        private static final String _QueryUpdate = "update realtime set PointTag = ?, Value = ?, DateTime = ?";

PreparedStatement ps1 = bd.getConnection().prepareStatement(_QueryBuscaRealtime);
           ResultSet rs1 = ps1.executeQuery();
           while(rs1.next()){
            RealTime realtime = new RealTime();
            realtime.setPointTag(rs1.getString(1));
            realtime.setValue(rs1.getString(2));
            realtime.setDataGravacao(rs1.getString(3));
            listaRealtime.add(realtime);
          }
          for(int j = 0; j < listaRealtime.size(); j++){
            real = (RealTime) listaRealtime.get(j);
            String dataGravacao = real.getDataGravacao();
            if (dataGravacao != null){
              ps = bd.getConnection().prepareStatement(_QueryDeletarRealtime);
              ps.setString(1,real.getPointTag());
              ps.executeUpdate();
              ps.close();
            }
          }
          ps1.close();
          for (int i = 0; i < lista.size(); i++) {
            ps = bd.getConnection().prepareStatement(_QueryDeGravacao);
            cfh = (PointCFH) lista.get(i);
            String pointTag = cfh.getPoint_CD_Tag();
            plc = Integer.parseInt(cfh.getRtu_CD_PlcAddr());
            func =Integer.parseInt(cfh.getPoint_CD_TypeAddr());
            ender = Integer.parseInt(cfh.getPoint_CD_PointAddr());
            qn_HiCount = Integer.parseInt(cfh.getPoint_QN_HiCount());
            qn_LoCount = Integer.parseInt(cfh.getPoint_QN_LoCount());
            qn_Md_Hieng = Double.parseDouble(cfh.getPoint_MD_Hieng());
            qn_Md_Loeng = Double.parseDouble(cfh.getPoint_MD_Loeng());
            nCnt = 0;
            while ( ( (ret = dFEP.LeValorTag(plc, func, ender)) < 0) && nCnt < 3) {
              Pause(1);
              nCnt++;
            }
            CurDataHora = Calendar.getInstance().getTime();
            if (ret != 1) {
              if (TestaRede.Ping(ip_fep) != 0){
                System.out.println("NET ERROR - " + CurDataHora.toString());
              }
              ps = bd.getConnection().prepareStatement(_QueryDeGravacao);
              ps.setString(1, cfh.getPoint_CD_Tag());
              ps.setDouble(2, 0);
              ps.setTimestamp(3, null);
              ps.executeUpdate();
              System.out.println("FAIL READ TAG PLC=" + plc + ";FNC=" + func +
                                 ";END=" + ender + " - " + CurDataHora.toString());
            } else {
                value = qn_Md_Loeng +
                        ( ( (qn_Md_Hieng - qn_Md_Loeng) / (qn_HiCount - qn_LoCount)) *
                        (ret - qn_LoCount));
                Date d = new Date();
                datatual = new Timestamp(d.getTime());
                ps.setString(1, cfh.getPoint_CD_Tag());
                ps.setDouble(2, value);
                ps.setTimestamp(3, datatual);
                ps.executeUpdate();
                ps.close();

                ps = bd.getConnection().prepareStatement(_QueryHistory);
                ps.setInt(1,0);
                ps.setString(2,cfh.getPoint_CD_Tag());
                ps.setTimestamp(3,datatual);
                ps.setDouble(4, value);
                ps.setString(5, cfh.getPoint_NM_Unit());
                ps.executeUpdate();
                ps.close();
            }
          }
          ps.close();
          bd.getConnection().close();
          }
          catch (ClassNotFoundException ex1) { }
          catch (SQLException ex1) {
            System.out.println(ex1.getErrorCode());
            ex1.printStackTrace();