Data Quality, Data Maintenance
I read an interesting tidbit about data the other day: the United States Postal Service processed more than 47 million changes of addresses in the last year. That’s nearly 1 in 6 people. In the world of data, that factoid is a simple example of the challenge of addressing stale data and data quality. The idea of stale data is that as data ages, its accuracy and associated business rules can change.
There’s lots of examples of how data in your data warehouse can age and degrade in accuracy and quality: people move, area codes change, postal/zip codes change, product descriptions change, and even product SKUs can change. Data isn’t clean and accurate forever; it requires constant review and maintenance. This shouldn’t be much of a surprise for folks that view data as a corporate asset; any asset requires ongoing maintenance in order to retain and ensure its value. The challenge with maintaining any asset is establishing a reasonable maintenance plan.
Unfortunately, while IT teams are exceptionally strong in planning and carrying out application maintenance, it’s quite rare that data maintenance gets any attention. In the data warehousing world, data maintenance is typically handled in a reactive, project-centric manner. Nearly every data warehouse (or reporting) team has to deal with data maintenance issues whenever a company changes major business processes or modifies customer or product groupings (e.g. new sales territories, new product categories, etc.) This happens so often, most data warehouse folks have even given it a name: Recasting History. Regardless of what you call it, it’s a common occurrence and there are steps that can be taken to simplify the ongoing effort of data maintenance.
- Establish a regularly scheduled data maintenance window. Just like the application maintenance world, identify a window of time when data maintenance can be applied without impacting application processing or end user access
- Collect and publish data quality details. Profile and track the content of the major subject area tables within your data warehouse environment. Any significant shift in domain values, relationship details, or data demographics can be discovered prior to a user calling to report an undetected data problem
- Keep the original data. Most data quality processing overwrites original content with new details. Instead, keep the cleansed data and place the original values at the end of your table records. While this may require a bit more storage, it will dramatically simplify maintenance when rule changes occur in the future
- Add source system identification and creation date/time details to every record. While this may seem tedious and unnecessary, these two fields can dramatically simplify maintenance and trouble shooting in the future
- Schedule a regular data change control meeting. This too is similar in concept to the change control meeting associated with IT operations teams. This is a forum for discussing data content issues and changes
Unfortunately, I often find that data maintenance is completely ignored. The problem is that fixing broken or inaccurate data isn’t sexy; developing a data maintenance plan isn’t always fun. Most data warehouse development teams are buried with building new reports, loading new data, or supporting the ongoing ETL jobs; they haven’t given any attention to the quality or accuracy of the actual content they’re moving and reporting. They simply don’t have the resources or time to address data maintenance as a proactive activity.
Business users clamor for new data and new reports; new funding is always tied to new business capabilities. Support costs are budgeted, but they’re focused on software and hardware maintenance activities. No one ever considers data maintenance; it’s simply ignored and forgotten.
Interesting that we view data as a corporate asset – a strategic corporate asset – and there’s universal agreement that hardware and software are simply tools to support enablement. And where are we investing in maintenance? The commodity tools, not the strategic corporate asset.
Photo courtesy of DesignzillasFlickr via Flickr (Creative Commons license).