Hi Jose,
You can see program documentation by clicking Info button within the transaction.
You can also see the following links:
2009024 - Year-End Postings in RFSUMB00, FAGL_YEC_POSTINGS, FAGL_YEC_POSTINGS_EHP4
Closing-Opening Postings at Year End (RFSUMB00) - ERP Financials - SCN Wiki
Best regards!