d924f03e_sselaer_Data_Warehouse_Project__data_warehousing_systems
[operational systems] Operational systems are generally application-specific, resulting in a multitude of partially or non-integrated systems and redundant data (e.g. billing data is not integrated with payroll data). [data warehousing systems] 
Data warehousing systems are generally integrated at a layer above the application layer, avoiding data redundancy problems.
Operational Systems vs. Data Warehousing - Rensselaer Data Warehouse Project
data warehousing systems