What is a Source System
A source system is a system organizationally determined to be a source where core data elements are maintained. A source system is the authoritative data source for a given data element. Source systems include systems of record.
For example, a registration system or an accounting system could be a source system. Conversely, a data warehouse is not a source system. Data flow from disparate source systems like registration and accounting systems into a data warehouse. A data warehouse can be the source of data for reporting but a data warehouse is not a source system.