How do I read this "standard" table in my Function Module?

Question

I have a remote-enable Function Module (RFC).  I am receiving two tables as part of the parameters.  Table "A" is header information, and Table "B" is detail information.  So for every 1 "A" header record, I may have 1 to many "B" detail records.  I have a field we'll call "vendor_number" that is the common link between the two tables.
Here's what I want to do:  I want to loop through table "A", and for each record, I want to do a READ on table "B", using the "ref_doc_no" from "A" as my key, to get the position of the first matching record.  I hold onto the value of the table index and then start looping table "B", adding 1 to the saved table index each time to process all of the detail records.
Here's the problem:  This worked great as an ABAP program.  I had my "B" table declared with "ref_doc_no" as a non-unique key.  But when I ported my code over to the RFC, it told me that the RFC could only deal with standard tables.  I had to remove the "ref_doc_no" key declaration.  So now when I try to activate, I get an error similar to this:
The declaration for the key field "another_field" is incomplete; however, "another_field" is contained in the key of table "B" and must be filled.
I don't understand that.  I've not declared any keys for table "B".  I don't understand why it's thinking I need to populate "another_field" (I don't even know what the value would be).  My code to read the table (i.e. the line getting the error) is this:
Priming read on table (sets the initial sy-tabix index value)
    READ TABLE it_incoming_invoice_line_item "table 'B'
      WITH TABLE KEY ref_doc_no =
                     wa_incoming_invoice_header-ref_doc_no
                INTO wa_incoming_invoice_line_item.
Is it possible for me to do some sort of direct read on a table in an RFC?  The only alternative I can think of would be to have to loop through table "B" until I find the first occurrence of a match.  Is that what I need to do?
Thanks everyone.  Points, as always, awarded for helpful answers.

Answer 1

Dave,
1. You can fire SELECTS in an RFC as well, but in your case the data exists in SYSTEM A and the RFC is in System B, so you can't do that. You can fire SELECTS on tables in the same system.
2. Quick example of two table loops - EKKO (HEADER) EKPO (ITEM).
LOOP AT EKKO.
LOOP AT EKPO WHERE EBELN = EKKO-EBELN.
ENDLOOP.
ENDLOOP.
I hope this is clear now.
Regards,
Ravi