Debit memo procedures and payment order Lot

Hi experts,

First of all thank you for your help in the last weeks.

I have two questions:

1.Can anybody explain me what the debit memo procedures is and how to use it with payment order Lot ?

When can we exactly use Payment order Lot (t-code PF45)?

2.As we know, we can process payment lot auomatically, check lot automatically.

How do I set up this in SPRO ? How do I read then payment data in SAP, is it from a file ?

Thanks in advance,

Thierno