ConfigFileAndroid config = DatabaseManager.createConfigurationFileAndroid("data.udb", this);

conn = DatabaseManager.connect(config);

private int getLastId(Connection conn) {

int baseId = 0;
try {
        PreparedStatement ps = conn
                .prepareStatement("SELECT MAX(idState) as maxIdState FROM bzState");
        ResultSet rs = ps.executeQuery();
        rs.next();
        String lastId = rs.getString("maxIdState");
            if (lastId != null)
            baseId = Integer.parseInt(lastId);
        rs.close();
        ps.close();
    } catch (Exception ex) {
    }
    return baseId;
}

private Connection createConnection() throws ULjException {
    ConfigFileAndroid config = DatabaseManager
            .createConfigurationFileAndroid(
                    "mSeries_model.udb", this);
    return DatabaseManager.connect(config);
}

private void concurrentTransactions() throws Exception {
    int lastId = 0;
    Connection conn1;
    Connection conn2;
    Connection conn3;
    // conn1 used to check the current last id.
    conn1 = createConnection();
    lastId = getLastId(conn1);
    // conn2 used to create and commit a new row.
    conn2 = createConnection();
    // conn3 used to create and roll back a new row.
    conn3 = createConnection();
    // Insert a new row in the table: conn1 / lastId + 1
    conn2.prepareStatement(
            "INSERT INTO bzState VALUES (" + (lastId + 1)
                    + ", 'ZZ', 'ZZZZ')").execute();
    // Insert a new row in the table: conn2 / lastId + 2
    conn3.prepareStatement(
            "INSERT INTO bzState VALUES (" + (lastId + 2)
                    + ", 'ZZ', 'ZZZZ')").execute();
    // Check the last id.
    int tempLastId = getLastId(conn1);
    if (tempLastId != lastId) {
        throw new Exception("No committed transactions.");
    }
    conn2.commit();
    conn2.release();
    // Check the last id.
    tempLastId = getLastId(conn1);
    if (tempLastId != (lastId + 1)) {
        throw new Exception("First transaction committed.");
    }
     conn3.rollback();
    conn3.release();
    // Check the last id.
    tempLastId = getLastId(conn1);
    if (tempLastId != (lastId + 1)) {
        throw new Exception("Second transaction rolled back.");
    }
}

public void onClick(View v) {
    try {
        concurrentTransactions(); // OK.
        concurrentTransactions(); // OK.
        // If we close the application and run again it fails.
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}