I recently got to know this wonderful tool when upgrading an old Sitecore version. The tool itself allows you to migrate any Sitecore 6.6 or Sitecore 7.2 versions to Sitecore 8.2. It also includes support for migrating Web Forms for Marketers.
My first experience was upgrading a 7.2 to 8.2. and within a day, the solution was fully upgraded and ready for testers. However, my newest attempt at upgrading a 6.6 solution gave a bit trouble. We decided to run at test upgrade to see if everything was migrated as it should, locally first.
All seemed fine, and we ran the migration again, but from using the production environments databases. This time the tool skipped both Security and Configuration. LEaving all users and roles behind. After some debugging and searching, I found that this was a know issue with the Express Tool:
The tool skips security and configuration steps if at least one migration was completed for the same source version (137519). Source
We needed to reset the tool in order to be able re-run the migration. To reset the tool you have to delete the Database file, created during the first run of the tool:
It is located in the root folder of the tools. The database file stores information on previous migrations, and somehow Sitecore skips Security and Configuration, if you already migrated the source version once before.
With the tool reset, the migration works perfectly again 🙂