Before embarking on a large scale data migration from a legacy system into a new system, it is important to establish a game plan.  Part of the game plan is to profile the data that will be migrated.  Unfortunately, too many times I see Data Analyst diving into the source database and begin writing extensive SQL queries that provide various permutations of data profiling reports before determining if the data is even relevant to the new system.   I believe that by having a game plan for data profiling and subsequently, establishing a remediation plan, the organization will save a lot of time and money.