How Data is Moved When a Forest is Retired from the Database
If a rebalancer-enabled forest is retired, the rebalancer empties the forest by “balancing out” all of the documents to the other forests attached to the database. The rebalancers on other forests re-calculate document routing as if the retired forest no longer exists. For new inserts, the retired forest is excluded from consideration by the document assignment policy.
Note
Retire is a separate operation from detach or delete. A read-only forest cannot be retired. To preserve all of the documents in the database, you must first retire a forest to rebalance the documents on the remaining forests in the database before detaching that forest.