As like as PO, Invoice screen contains also a header level and a item level.
Item level contains all the item of reference document.
And all the item can contains different different value, tax, quantity etc etc.
And its also save different line item into RSEG table.
How can you clubbed the all line item?
This is not a business logic.
Any way about your system performance.. You can drop a mail to you administrator or basis team to improve the system performance.
Message was edited by: Dev Patra