The TFS Integration Tools offer us user value mapping and the Lookup Service when we need to map users from the source to the target systems. While options are great, we need to decide when to use one or the other or both of these technologies.

Let’s explore some common scenarios we can encounter in the world of migrations:

Scenario 1

All users are the same on the source and the target, either in same domain, different domain or different systems. Version Control and/or Work Item Tracking data is moved.
Scenario 2

All users are different on the source and the target. Version Control and/or Work Item Tracking data is moved.
Scenario 3

Most users are the same on the source and the target, but some are different or not available. Version Control and/or Work Item Tracking data is moved.
Scenario 4

Scenario 1, 2 or 3 moving only Work Item Tracking Data, with only a handful of users.
 

Now .. when do we use one or the other, or both?

Think of the lookup service as a superset of the value mapping approach, which works for both version control (VC) and work item tracking (WIT) data. In comparison, the value mapping is a very explicit user to user mapping for WIT-only data.

The lookup service allows you to define rules that can easily express a relationship for thousands of users in a cross-domain move, allows you to map the display name instead of domain/user pairs; and also allows you to disable the Active Directory search to enforce a static user transformation.

Once we understand the difference between the two technologies, we can conclude that the lookup service is capable to deal with all four scenarios. The value map is a WIT-only quick and dirty way to map a handful of user names, which could be considered for scenario 4.

For further information see the configuration guide that ship as part of the product, or see What is the Lookup Service? Q&A-27 and What is the Lookup Service? Q&A-27 Errata 1.

Once again it becomes apparent that the planning of the migration and  the testing of the proposed configuration is important to understand the technology, the configuration options and the impact and limitations thereof.

Related Information: When you are migrating across domains, also take not of Cross Domain Migration … now what? Q&A-11.