Guide to Data Warehousing and Business Intelligence
The Data Warehouse Staging Area is temporary location where data from source systems is copied.
A staging area is mainly required in a Data Warehousing Architecture for timing reasons. In short, all required data must be available before data can be integrated into the Data Warehouse.
Due to varying business cycles, data processing cycles, hardware and network resource limitations and geographical factors, it is not feasible to extract all the data from all Operational databases at exactly the same time.
For example, it might be reasonable to extract sales data on a daily basis, however, daily extracts might not be suitable for financial data that requires a month-end reconciliation process.
Similarly, it might be feasible to extract "customer" data from a database in Singapore at noon eastern standard time, but this would not be feasible for "customer" data in a Chicago database.
Data in the Data Warehouse can be either persistent (i.e. remains around for a long period) or transient (i.e. only remains around temporarily).
Not all businesses require a Data Warehouse Staging Area. For many businesses it is feasible to use ETL to copy data directly from operational databases into the Data Warehouse.