One of the key challenges that any designer of a data warehouse has to face is the design of the overnight processing. There are a number of major issues that need to be addressed, if this is not to become a stumbling block to the success of the data warehouse. The key issue is keeping to the time window and ensuring that you do not eat into the next business day. The sheer volume of work that has to be accomplished, and the serial nature of many of the operations, make this more difficult than it may first seem.