How can i append data at the same time getting ajax response from server.?

How can i append data at the same time getting ajax response from server.?

Anyone can help me.
I'm working in Jquery-mobile with phonegap application.
How can i append data at the same time getting ajax response from server? Here more than 800 kb data is retrieved from the server as Json format

This is my code:

    $.ajax({
        url:url,
        data:'',
        contentType: "application/json; charset=utf-8",
        type: "POST",
        dataType: "json",
        crossDomain:true,
        cache: false,
        async:false,
        //success: loadAllCars,
        
        success:function(data){
           //alert(data)
        },
        error: OnError
    });

I want to fetch data at the same time which getting from server  for example:

I have more than 800 KB size of data and when it's get 10 KB size data of 800 KB and i need to fetch that at the same time for decrease the delay of appending and avoid the user waiting