This document provides an overview of foreign currency valuation in SAP, including:
1) How general ledger accounts are valued based on master data setup, using exchange rate keys like KDB and KDF to determine gain/loss accounts.
2) The FAGL_FC_VAL transaction which performs the valuation and posts amounts to the appropriate accounts.
3) Details on open item versus non-open item valuation and how differences are handled over time in the general ledger.