Persistence in Data Warehousing

Persistence of redundant data in Data Warehouses is often simply justified with an achievement of better performance when accessing data for analysis and reporting. However, there are other reasons to store data persistently, which are often not recognized when designing Data Warehouses. As processing and maintenance of data is complex and requires huge effort, less redundancy downsizes effort. Latest in-memory technologies enable good response times for data access. That arises the question, what data for what purposes really need to be stored persistently. We present a compendium of purposes for data persistence and use it as a basis for decision-making whether to store data or not.