The vertical scrollbar on the ICEFaces ace:dataTable is flakey, though pagination works fine. This is apparently also true of PrimeFaces, and probably other JSF frameworks. To enable a scrollbar without pagination, a workaround is to set scrolling=false, and then wrap the datatable in a div:
<div style="overflow:auto;width:100%;height:180px;">
<ace:dataTable ...>
</ace:dataTable>
</div>
