The Data Warehouse ETL Toolkit by Ralph Kimball & Joe Caserta

Author:Ralph Kimball & Joe Caserta [Kimball, Ralph & Caserta, Joe]
Language: eng
Format: epub
ISBN: 9781118079683
Publisher: Wiley
Published: 2011-04-21T05:00:00+00:00

Physically Deleting Facts

Physically deleting facts means data is permanently removed from the data warehouse. When you have a requirement to physically delete records, make sure the user completely understands that the data will never be able to be retrieved once it is deleted.

Users often carry a misconception that once data enters the data warehouse, it is there forever. So when users say they will never have a reason to see deleted data, never and see need to be clarified. Make sure they say exactly what they mean and mean what they say.

Never. It is quite common for users to think in terms of today’s requirements because it is based on their current way of thinking about the data they use. Users who’ve never been exposed to a data warehouse may not be used to having certain types of history available to them. There’s an old aphorism: You can’t miss what you’ve never had. In most cases, when a user says never, he or she means rarely. Make sure your users are well aware that physical deletion is a permanent removal of the record.

See. When a user says see, most likely he or she is referring to the appearance of data in reports. It’s quite common that users have no idea what exists in raw data. All data is usually delivered through some sort of delivery mechanism such as business-intelligence tools or reports that may be automatically filtering unwanted data. It’s best to check with the team responsible for data presentation to confirm such requirements. If no such team exists, make sure your users are well aware that physical deletion is a permanent removal of the record in the data warehouse.

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