If the server crashes while a partial update is being applied, when the MDEX Engine starts up again, it will go through its list of generation files to determine if any generation file is in a bad state. If any are bad, the MDEX Engine will automatically delete them before applying the next partial update. In other words, no manual intervention is required in the MDEX Engine's generations directory (and any user modification to the generation files in an attempt to rollback the generations is not supported).