Non-exchange required, partner will be the &

What causes this issue?

Normally the system takes information on the partner (Purchasing =
Vendor, Sales = Customer) from the quantity schedule data if the qty.
schedule data is assigned to an exchange agreement. In this case, the
quantity schedule does not contain partner data for non-exchange
documents. For this kind of situation, the purchasing/sales document
header table must be read to get partner information.

System Response

Tables for each quantity schedule item have to be read.
If the indicator "List additional fields" is set, the system reads the
document header table; thus, the partner (vendor/customer) is listed,
otherwise the partner is the "Exchange partner", meaning that the
partner information is initial.

How to fix this error?

Check your input, particularily the partner field and option "list all,
only exchange, only without exchange" and the option "List additional
fields".
Set the partner information on the selection screen to initial, if the
partner information is not important for your purposes, then you will
get a list without partner information.
Confirm the current situation by pressing "enter" if you are interested
in partner information for assigned documents which are not related to
Exchanges.
Remove the indicator "List additional fields" or initialize the
selection field "Exch.Partner" if you are not interested in partner
information.

Error message extract from SAP system. Copyright SAP SE.