A data warehouse is a central storage for all data that an enterprise’s various business systems collect. Developing a data warehouse includes production of systems that can extract data from operating systems and integrate data from one or more disparate sources. Additionally, the installation of a warehouse database system provides users flexible access to the data.
Data warehouses possess five key characteristics:
I. Data from multiple operational databases is combined.
II. Data is certified to be of higher quality. Low-quality data is cleansed before entering the warehouse.
III. Data is read-only. It cannot be changed by end users.
IV. Data is historical and represents a series of snapshots depicting the state of businesses at different points in time.
V. Data warehouses are frequently large and usually in the multi-gigabyte range.
There are two different approaches to data warehousing: top down and bottom up. The top down approach spins off data marts for specific groups of users after the complete data warehouse has been developed. The bottom up approach builds data marts first, then combines them into one data warehouse.
There are many benefits of data warehouses. They provide the opportunity to:
Collect data from multiple sources into one database so a single query engine can be used to present data
Improve the quality of data
Provide a single common data model for all data regardless of the data’s source
Maintain data history
Make decision-support queries easier to write
Restructure the data to be easily understood by business users