AX 2009 Multiple datasource join mode improve performance

Dear seniors,

I need a guide on how to improve the performance for my current form.

-VendInvoiceJour (Form)

-VendInvoiceJour (Datasource)

-VendInvoiceTrans (Datasource)

-InventDim (Datasource)

-VendTable (Datasource, newly added, LinkType::OuterJoin) -Reason to add this datasource is to get a particular field value from vendTable.

-Dimensions (Datasource, newly added, LinkType::OuterJoin) -Reason to add this datasource is to get a particular field value from Dimensions.

My problem is there is slow performance when I include 2 new datasource into the form.

Once I open the form and the scrolling point turn out to be lagging.

Could anyone know the reason why its so slow on the performance once the additional datasource been added to the form?