Change Topology Manager mapping on SDL Web 8
# A the publication id in a TtmMapping cannot be changed. The API does not allow changing the publication id since
# changing it would break the publish status in the Content Manager.
# The old mapping s
# 1. First unpublish everything from the publication holding the old mapping. Or decommission the publishing target if
# the Content Broker changed and the content cannot be unpublished.
# 2. Lookup the TtmMapping Id, PublicationId WebApplicationId and RelativeUrl (optional) of the old TtmMapping
Get-TtmMapping
# 3. Remove the old mapping
Remove-TtmMapping -Id Mapping6
# 4. Add a the new mapping
Add-TtmMapping -PublicationId 'tcm:0-5-1' -WebApplicationId 'Website1_RootWebApp' -RelativeUrl '/en'