RE: We're shutting down Dynamics CRM - how do we archive the data? Attachments especially
Hi Michael,
Thank you for the post.
Regarding the data inside Dynamics, I had achieved a couple of months ago during an internal assessment something very similar with what you want using flows.
As you are an on premises customer, this will not be possible for you, but here are some ideas on how to get the data out of the system.
You can develop a console app to retrieve the data, the way you need to implement it is the following:
You will go ahead and use crmserviceclient to connect to the organization and from there you will retrieve your data keeping in mind the attachments are encoded, therefore you need to decode them first.
Once you have your data out stored somewhere else you can go ahead and turn off the system.
Just for reference, I had performed an Web API query in order to get the content of a Note having an attachment and this is how it looks like:

The description of that Web API query is below:
https://docs.microsoft.com/en-us/dynamics365/customer-engagement/web-api/annotation?view=dynamics-ce-odata-9
If you do not have a version 9 system, please change the v9.0 with the first two sets of digits you have within your About section of the system, corresponding with the version.
There are some other options to achieve this functionality, including some Microsoft Labs and third party solutions which will store your data somewhere else like Azure Blob or even SharePoint, but it really depends on your infrastructure.
Good luck!