Mandatory Grouping Attributes for Auto Invoice

Hi Experts,

How can know what are the mandatory grouping columns that are picked by auto invoice  to create a transaction . This is because I am facing an issue where the Freight lines for an Order are getting split into two (order lines and freight) or three (order lines/two freight lines) transactions. So I need to check how the auto invoice is grouping these attributes and why is the ORDER invoice getting split into two or more invoices.

Note :The auto invoice is not scheduled and until and unless all the lines ,including Freight lines, get into the RA_INTERFACE_LINES_ALL , we apply a custom hold to the order.So all the lines for an order get inserted into the RA_INTERFACE_LINES_ALL all at once. There is no partial Invoicing done.