You should be very careful about purging data from both your OLTP systems and your business intelligence systems.
The reason: there are legal requirements for record retention, and you may be the custodian of the only copies of the data.
In the past, Accounting and Records Management professionals were responsible for record retention, focusing on physical documents, diagrams, and images. Microfilm and microfiche came along and provided the means to save storage space and improve access times, but the information was still in physical form. There are numerous suppliers of content management, document management, and records management systems that usually have the development and administration of record retention policies as features of their systems.
But today, especially with the boom in self-service web applications, there is a lot of data that never exists in physical form. It is entered by customers, suppliers, and employees, or generated automatically by EDI and supply chain systems. Collaborative systems are designed specifically so that information never is committed to any form you can "put your hands on." This means that the professionals who hold dominion over record retention policies and schedules have limited (or no) visibility or control over some forms of electronic data. Information Systems professionals have the responsibility to 1) maintain the data in a form that is consistent with the original form, 2) retain the data as required by legislation, regulation, or contract, and 3) destroy the data as required by legal counsel or the owners of the data.
So when transforming the data, purging the data, or making the decision to keep the data, take the time to understand the requirements of your records retention policies.
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