We used to have an interface who imported standard PO, with a contract number as PO number, then the number of lines was increasing. We had a first problem from 200 lines, we had to apply a patch, then the limit was about 900 lines. I made a few searches but this occurs 2 years ago and I'm not even able to find the SR or a patch number ...
But from a business point of view, it's obviously a bad idea to always have the same PO with a high number of lines (hard to match invoices, PO is never closed, etc.) , from this problem we choose to import PO with PO number generated from the BL number + an suffix (to avoid duplicates PO numbers)
Hope it helps a little,
May I know which version of Oracle when you encounter this issue?
I cannot find any related doc. or note in Support.Oracle.com mention the max. po line support in Oracle Purchasing.
Can I say 200 line should be safe in term of performance issue regardless of version ?
I don't think there is any limit for the PO line numbers, as I have seen POs with thousands of lines and performing well.