DataList in JSP - reload the session data

Session scope: Once loaded the dataList will persist during the session and won't be garbaged after one request in the same session. If you want to reload the session data every view to get the most recent data, then do as follows:

public List getDataList() {
        if (FacesContext.getCurrentInstance().getRenderResponse()) {
            loadDataList(); // Reload to get most recent data.
        return dataList;

The FacesContext#getRenderResponse() returns true when this getter is invoked during the render response phase. This is to prevent duplicate reloads as this getter can also be invoked during the apply request values phase or the process validations phase.

You can also consider to use two beans: one request-scoped bean for the views and form actions and one session-scoped bean for the session data. You can inject the session scoped bean in the request scoped bean as managed property using faces-config.xml. And in the request scoped bean you can invoke reload of the data after save/update/delete action of the session data.
Storing the data in the session scope has not only an impact on the server memory usage, but also on the user experience when the data is not for display only. Imagine what would happen with the data when the user manages (edit/delete) the data in multiple browser windows/tabs in the same session.
Instead of using the session scope you can also consider using the Tomahawk t:dataTable component. It has an extra attribute 'preserveDataModel' which you should set to true. This will store the datatable value in the component tree state in session and restore it during the next request. This way you can also avoid unforeseen concurrent updates on the datamodel in between the requests.