What happens if the SQL persistence database is not available during a forest recovery, what will the possible impact be?
The ForestRecovery-Persistance database is used to keep track of the steps in the forest recovery process in case the console crashes and needs to pick up where it left off, this is stored in the SQLDBNAME_PERSISTENCE.
RMADFE/RMADDRE can also be used successfully without Persistence DB, but the Persistence functionality will be lost.
The persistence DB only comes into play if you have to restart the recovery process, it is not advisable to run a domain or forest recovery without it, If the process gets interrupted for some reason, we may never be able to recover from it.