Term Usage (Usable, Not Usable, Retrievable but Not Usable, and Do Not Delete) can be updated in bulk using the Bulk Update of Term Usage Control tool.
Update Term Usage Controls
1.Go to the Tools menu > Authority Tool > Bulk Update of Term Usage Control
2.Enter the file name (or ID) for the Authority file in which you wish to perform the bulk update.
3.Enter the List name, or click on the Options button 
to select a list.
If you do not specify a List the update will be performed on all records.
3. Tick the update Usage attribute checkbox and choose your term usage control, or tick the Update delete attribute checkbox and choose whether the term can be deleted.
4. Press the Update button.
