Entry criteria to start DW project

If you had a recent major implementation with the Source Systems to Data Warehouse, it will make sense to wait for few months. This is because there is a natural cycle for system to settle down. However if there is routine state of instability in the source systems, one should embark upon the data warehouse project. This will lead to more painful data extraction and transformation process. The advantage is that it will only help identify the issues in the source systems as well as providing a cleaner information source for your enterprise reporting.

Some possible advantages of starting a data warehouse initiative in an unhealthy source system landscape:

• A good proportion of the effort you will spend in ETL (data profiling of the source system, extraction and transformation routines) will help you to address the data quality issues of the source system. You may identify some quick fixes to address data quality in source systems.
• You will create a more reliable source for business reporting, as Data warehouse data will be cleaner. Your data warehouse initiative itself might have been triggered due to the instable source systems. This will in future move your reporting to data warehouse, as it being a more reliable source. Also when you embark upon the data quality program for the source systems, you will be more educated on the root causes and possible solutions.
• As you work on ETL, you will get an opportunity to the level of mess and reasons for bad data quality (or instability) in the source systems. This will accelerate management focus on the issues, and prompt more funding in that direction.

Here are the recommendations to get the advantage out of above-stated approach

• Don't over commit and start small. If your source systems are relatively unstable, you may have risk of failing in building robust ETL. We recommend to start small with more stable systems.
• Ensure active engagement with people who 'know the secrets'. Have a greater connect and linkage with IT and Business specialists (more than what you would have done with the stable systems). These folks would be able to guide you on the weak areas, and will also share the 'bandages and crutches' which have been putting on the system.
• Ask for more than estimated time for ETL phase .