Data warehouse Layer

There is no widespread agreement on exactly what constitutes a data warehouse architecture. Though they may not be contradictory, views differ as to the relative importance of the possible components. One possible conceptualization of a data warehouse architecture consists of the following interconnected layers:

Operational database layer

The source data for the data warehouse

Informational access layer

The data accessed for reporting and analyzing and the tools for reporting and analyzing data

Data access layer

The interface between the operational and informational access layer

Metadata layer

The data directory (which is often much more detailed than an operational system data directory).

Benefits of data warehousing

• A data warehouse provides a common data model for data, regardless of the data's source. This makes it easier to report and analyze information than it would be if multiple data models from disparate sources were used to retrieve information such as sales invoices, order receipts, general ledger charges, etc.
• Prior to loading data into the data warehouse inconsistencies are identified and resolved. This greatly simplifies reporting and analysis.
• Information in the data warehouse is under the control of data warehouse users so that, even if the source system data is purged over time, the information in the warehouse can be stored safely for extended periods of time.
• Because they are separate from operational systems, data warehouses provide fast retrieval of data without slowing down operational systems.
• Data warehouses facilitate decision support system applications such as trend reports (e.g., the items with the most sales in a particular area within the last two years), exception reports, and reports that show actual performance versus goals.
• Data warehouses can work in conjunction with and, hence, enhance the value of operational business applications, notably customer relationship management (CRM) systems.