Roll back a migration

A migration changes files in a pull request, so you roll it back the way you roll back any change.

1. Revert the migration's pull request in the documentation repository.
2. Remove the redirect file the migration added, if it was published.

   Old URLs then resolve to the DITA-OT site again.

3. Optional: If an approved rule caused the problem, reject it so the next run doesn't use it.