Read and write large CLOB files from database Faster

I have a task to read CLOB files from Oracle 9i Database and write them to files. What I have works for small files but in cases of larger files, around 200MB this is taking around 5 hours for one file which is completely unacceptable. I am sure this can be done faster but I am not sure how. This is what I have:

//get the Clob record from the database and convert it to String
 public String getClobRecord() {
        Connection conn;
        Clob xmlCont;
        ResultSet rset;
        PreparedStatement stmt;
        try {
            conn = db.prepareConn();
            String sql = "select a.clob_clm from xml_statement a where period_id = ?";
            stmt = conn.prepareStatement(sql);
            stmt.setInt(1, pid);
            rset = stmt.executeQuery();
            while (rset.next()) {
                xmlCont = rset.getClob(1);
                xml = ClobStringConversion(xmlCont);
            }

            stmt.close();
            DBConnect.closeConn(conn);
        } catch (SQLException asd) {
            log.fatal(asd.getMessage());
        } catch (IOException asd) {
            log.fatal(asd.getMessage());
        }
        return xml;
    }
//My CLOB to String Conversion Method
  public static String ClobStringConversion(Clob clb) throws SQLException, IOException {
        if (clb == null) {
            return "";
        }
        StringBuilder str = new StringBuilder();
        String strng;
        BufferedReader br = new BufferedReader(clb.getCharacterStream());
        while ((strng = br.readLine()) != null) {
            str.append(strng);
        }

        return str.toString();
    }
//Write the String to File
public void writeXmlToFile(String fileDir, String xmlFileName) {
        File xmlfile = new File(fileDir + "/" + xmlFileName);
        xml = this.getClobRecord();
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(xmlfile));
            bw.write(formatXmlFile());
            bw.close();
        } catch (IOException asd) {
            log.fatal(asd.getMessage());
        }
    }

What Exactly Should I change to Accomodate very Large CLOB files? EDIT: A smaller sample of the resulting file: