Are there any requirements to drop all obsolete data from former migrated systems (like former system IDs in any added attributes/columns)?
My main argument on that topic has stayed the same through 25 years of software consulting and development:
Storage is cheap, CPU time is expensive. And I’d like to add: Project time is expensive, too.
Regarding Documentum SysObjects’s approximately 90 attributes there should really be no long talk about one additional 16-characters attribute. Just discussing the pros and cons as well as all required additional migration tasks, programs and workarounds to keep object IDs against all odds will quickly exceed the costs of that new database column storage.
Finally, long time running Documentum workflows (active: workflow state indicates document state) have to be checked for data integrity. The object model shows references by object IDs from workflows through tasks and packages to the submitted document. Document object ID change due to migration will cause problems here. Additionally, active workflows are hard to migrate: How to map a workflow template or model in a new target repository and how to map “approval users” of active tasks?
The best solution is to use migration events to review those long time running workflow templates! It is usually better to use a lifecycle to manage document states. Doing this you will be able to use simpler workflows (the so called quick workflows) to switch the document’s lifecycle state.
At migration day, there should be a very small number of active workflows. The important document state information of all other documents is persistent through their lifecycle state and managed independently from any object ID. By the way: This is also covered by fme migration-center features.
I learned this from a real project: Before migration day, there was a business advisory to complete or cancel all active workflows. Estimated efforts for later restarts for that small number of running workflows were so small that other workarounds were not worth a discussion.