Data Warehouse

Data warehouse is a repository of an organization's electronically stored data. Data warehouses are designed to facilitate reporting and analysis

Data warehouse architecture

• Operational database layer

The source data for the data warehouse - An organization's Enterprise Resource Planning systems fall into this layer.

• Data access layer

The interface between the operational and informational access layer - Tools to extract, transform, load data into the warehouse fall into this layer.

• Metadata layer

The data directory - This is usually more detailed than an operational system data directory. There are dictionaries for the entire warehouse and sometimes dictionaries for the data that can be accessed by a particular reporting and analysis tool.

• Informational access layer

The data accessed for reporting and analyzing and the tools for reporting and analyzing data - Business intelligence tools fall into this layer.

Benefits of data warehousing

• A common data model which makes it easier to report and analyze information than it would be if multiple data models 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.
• The information in the warehouse can be stored safely for extended periods of time.
• Data warehouses provide retrieval of data without slowing down operational systems.

Disadvantages of data warehouses

• Not the optimal environment for unstructured data.
• There is an element of latency in data warehouse data.
• Maintenance costs are high.
• Data warehouses can get outdated relatively quickly.
• Duplicate of functionality that must be developed in the data warehouse in the operational systems