A customer has been using Marketing Cloud with data imported from an external system. This data is to be migrated to a new SF CRM which will become the new source database via the MC connector and the CRM identifier the new identifier. The customer would like to keep the existing tracking data in Marketing Cloud. Suggestions to how to overwrite the exisiting identifier in order to maintain tracking data in the platform?

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    The only possible solution for this (outside duct taping something together by exporting current tracking and storing elsewhere for reference) would be to talk with SF Services. I believe they can update subscriberkeys in certain situations, but do know it is likely going to cost $$$$, especially as you are doing essentially all of your subscribers. Feb 7, 2023 at 14:47
  • Thank you Gortonington
    – Emma
    Feb 8, 2023 at 12:24

2 Answers 2


The only solution for achieving this, is (as Gortonington rightly states), a subscriber key migration. This is a paid engagement done by Salesforce professional services. I have described it in this article. But the main points is:

When looking into migrating to a new Contact Key, most of the projects I have worked on, are not willing to take on the task of Subscriber Key migration. They either are not willing to invest the money, or accept the downtime (of up to 24 hours). Instead they update the data within all relevant data extensions, to include the new Subscriber Key. However all the historical engagement data in e.g. data views, and tracking reports will be lost, as well as journeys which are set to no-reentry will accept same contacts, as exclusion is based on Contact Key.

You will be able to retain all the historical engagement data by using Tracking Extract in Automation Studio, and store the data in data extensions, where you will be able to update the Subscriber Key originating from the data views, and replace it with the ID from SF CRM.

  • I suspected this was the case. Many thanks Lukas.
    – Emma
    Feb 8, 2023 at 12:25

I don't think it's possible to migrate your old tracking data to the new identifiers in your MC account, or at least I have never heard about it before.

In my opinion, the best way is to find a way to extract this tracking data so that it can be used for your analytics later. 

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