A “Mapping” in Oracle Data Integrator is a business rule implemented as a SQL clause. It is a rule that maps one or more columns from one or more source datastores onto one of the target datastore column.
It can be as simple as stating that the CUSTOMER_NAME column from the CUSTOMER dimension table corresponds to the NAME column of the HZ_PARTIES from the transactional system. It may also be as complex as calculating aggregates or operations on multiple columns in various datastores located even on different severs. Oracle Data Integrator includes an expression editor which helps you build the mapping.