Write notes on the following: Characteristics of data warehouse.

A data warehouse is a storage area for processed and integrated data across different sources. The distinct features of a data warehouse are: Subject-oriented: A data warehouse is organized around major subjects such as customer, products, sales, etc. Integrated: A data warehouse is usually constructed by integrating multiple, heterogeneous sources. When data is moved into the data warehouse, it assumes a consistent coding convention. Data cleaning and data integration techniques are applied to maintain consistency in naming conventions, measures of variables, encoding structures, and physical attributes. Non-volatile: A data warehouse is always a physically separate store of data, which is transformed from the application data found in the appropriate environment. Due to this separation, data warehouses do not require transaction processing, recovery, concurrency control, etc. The data is not updated or changed in any way once it enters the data warehouse, but is only loaded, refreshed, and accessed for queries. Time-variant: Data is stored in a data warehouse to provide a historical perspective. The data warehouse contains data that are 5 to 10 years old, or older, to be used for comparisons, trends, and forecasting. Alternative Answer for 3A(iv) - Additional Characteristics: Data warehouse is a storage area for processed and integrated data across different sources which will be both operational data and external data. The distinct features of data warehouse are: Multidimensional conceptual view Generic dimensionality Unlimited dimensions and aggregation levels Unrestricted cross-dimensional operations Dynamic sparse matrix handling Client-server architecture Multi-user support Accessibility Transparency Intuitive data manipulation Consistent reporting performance Flexible reporting