We are migrating from one data warehouse to a new one. Which questions need to be asked to perform a technical analysis of the old environment in order to create a profile of the old data warehouse?


Sid Adelman's Answer: Most of the questions you need to ask go far beyond the technical. You need to get an understanding of the existing environment in each of the following areas:

  • Business value - How much is the existing data warehouse contributing to the business value of your organization?
  • Organization and culture - Is the existing organization properly supporting the data warehouse? If you are using contractors and consultants, are you getting the most out of them?
  • Development methodology - Is an appropriate development methodology in place and is it being used?
  • Architecture - Do you have the right architecture for performance, availability and growth?
  • Data warehouse data - Is the data all there? Is it clean? Do the users trust it?
  • Meta data - What meta data are you capturing? How is it being captured? Is it being used effectively?
  • Standards - What standards are in place? Are they being followed?
  • Modeling - What is being modeled and how are the models employed? Do the models automatically generate metadata?
  • Database design - Are the databases designed properly? Are you going through a database design review process?
  • Performance - What is the average response time? Are the users satisfied with the response time?
  • Software - Do you have the right software in place? How well is the software being used? Do the different software components work well together?
  • Vendor management - Are you getting the best support out of your vendors?

Clay Rehm's Answer: My first question is why are you moving from one data warehouse to another? Is this a business division request or a technical request? I assume you are moving for one or many good business reasons. If the reason is a technical reason, is it to reduce cost, increase performance or improve ease of use?

Having said that, increasing performance can be accomplished many ways. This would include modifying the database design (data model), adding/modifying indexes, partitioning, changing the network bandwidth, moving the database from one server to another, and so on. The solution can be one of these items or a combination of them.

I would suggest reading the book Data Warehouse Project Management by Adelman/Moss, and Impossible Data Warehouse Situations with Solutions from the Experts (multiple authors). These books cover the requirements gathering techniques you will need to accomplish your goal.

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