Offline Metadata Instances in SharePoint 2010 & OfflineTermstoreNames

If you're using powershell to add metadata to your termstore and you see only an entry in the OfflineTermstoreNames property, then it seems that some of your Metadata Services are offline.

C:\> $site = Get-SPSite http://mysharepoint/sites/project
C:\> $session = new-object Microsoft.SharePoint.Taxonomy.TaxonomySession($site) 
C:\> $session

To activate all instances open the SharePoint Management Shell and type:

C:\>$instance = Get-SPServiceInstance | ? {$_.TypeName -eq "Managed Metadata Service"}
C:\>$instace

It will now display all your instances. If the e.g. first and second are disabled, start it with:

C:\>$instance[0] | Start-SPServiceInstance #Start First
C:\>$instance[1] | Start-SPServiceInstance #Start Second

Wait few minutes. Grab the instance again and check if they are enabled:

C:\>$instance = Get-SPServiceInstance | ? {$_.TypeName -eq "Managed Metadata Service"}
C:\>$instace

Now all Termstores should be online.