Abstract: An apparatus and method for implementing data warehousing systems. According to a first embodiment, a system may include a plurality of data warehouses, and a data warehouse manager configured to extract data sets from one or more data sources for storage in one or more of the plurality of data warehouses. Each of a first subset including two or more of the plurality of data warehouses may be configured to store a respective replica of a first data set extracted by the data warehouse manager. Further, the data warehouse manager may be further configured to allow a query dependent upon the first data set to be evaluated by one of the first subset of data warehouses before each respective replica of the first data set has been stored to a corresponding data warehouse of the first subset.