In the insurance industry, the advantage of custom-built marts and warehouses ensures that the structure and queries match the data, but the customization makes it very difficult and expensive to maintain. On the other hand, off-the-shelf marts and warehouses maintained by the third party and are general and less useful than the custom ones. In either case, they can easily grow beyond anything manageable. This whitepaper focuses on providing an overview of data warehousing in the insurance industry.