RFDUZI00 Print Prog. extra functionality, Wht data is migrating?

Hi,

In ECC6.00 version SAP has given a extra funtionality of "Data Migration" in the program RFDUZI00 (Print prog for printing the SAP Script of "Notice sent to customers for charged interest amounts for their late due payment").

SAP is achieving this Data migration functionality by calling the FM FI_INTITHE_WRITE_FOR_MIGRATION, fine. But, I did not understand that, actually, What is SAP doing? where its writing the data(i guess the data is customer open items)? where its migrating? is it to data base?

I have seen WHERE USED LIST of this FM, I went into this FM and tried to understand, actually whts SAP doing inside this FM, I tried to pull the FM documentation, in Google as well, but nothing is success!! So, pls. let me know it.

Thank you