Apply Receipts when you have massive amounts of data

Hello,

On a daily basis we will recieve over 200,000 Rows of F03B11 Records, and one a weekly basis we will recieve reciepts that will need to be applied to these invoices.

We are using the RMR1 - Generic Match - FIFO method, which is doing exactly what we need.

The issue that we are having that the time to process these receipts grows every week. 

I notice that the Algorithm that is used didn't have any selection on the F03B11 records for ones paid and the open amount is equal to zero - R03B50B

The R03B551 - Takes for ever now.  There is a Business function B03B0169 that does record selection from the F03B11 -  I'm not a C person, but I feel it is pulling in every F03B11 that matches the RMR1 Generic Field Match record even if it is paid.