The most important step in the overnight processing is obtaining the data. This in itself is probably a simple operation; the problems arise when the data is delayed or cannot be transferred. The whole process depends on this step, and cannot complete until the data becomes available. The data transfer process should be designed, where possible, to work on subsets of the data. Any set of data that has no transformation, constraint or checking dependencies should be capable of being handled individually. The process must be designed to take this data as far through the overnight process as it can before hitting dependencies. Any time and resource saved early in the evening can be used later to speed up the process, or to catch up on lost time.