Thanks for your help.
However if I replace this line :
with this line :
The data is well refreshed however the vertical scroll is also reset I start reading the datagrid from the beginning. (It is the same action as the refresh button in the bottom toolbar).
Is there a better way to refresh only the current visible part of the grid?
The final idea is to use highlight color for each updated rows like this:
var row = grid.getView().getRow(rowIndex);
var el = Ext.fly(row);