Step-4: OLTP & Slowly Changing Dimensions

• OLTP systems not good at tracking the past. History never changes.
• OLTP systems are not “static” always evolving, data changing by overwriting.
• Inability of OLTP systems to track history, purged after 90 to 180 days.

Actually don’t want to keep historical data for OLTP system.

One major difference between an OLTP system and a data warehouse is the ability and the responsibility to accurately describe the past. OLTP systems are usually very poor at correctly representing a business as of a month or a year ago for several reasons as discussed before. A good OLTP system is always evolving. Orders are being filled and, thus, the order backlog is constantly changing. Descriptions of products, suppliers, and customers are constantly being updated, usually by overwriting. The large volume of data in an OLTP system is typically purged every 90 t o 180 days. For these reasons, it is difficult for an OLTP system to correctly represent the past. In an OLTP system, do you really want to keep old order statuses, product descriptions, supplier descriptions, and customer descriptions over a multiyear period?

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