it is known that using Ajax you can asychronously make calls to server with out reloading the whole page.
But what I have observed when using Ajax with faces (JSF) is that the whole page is submitted although the reloading happens for the specific part of the page. So how does really Ajax help in improving the performance?
I agree.. there may be a misunderstanding as to what should be happening with an AJAX request.
Ideally you make an AJAX request for a discrete piece of data.. like loading a page of records into a datagrid. The real advantage here is bandwidth. Even if the server runs through the entire execution lifecycle of the source document, the performance gain comes from
Fewer bytes transmitted
Client browser does not need to reinitialize the entire document (very slow)
Updates are made to the page via DHTML instead (very fast)
User gets to preserve their workflow, and page state overall.. which means more productivity for the user, and better perceived application performance.