Normally active directory once is corrupted best method is to repair the active directory. As IT administrator user has keep a proper backup either date wise or weekly wise.
Explanation:
If IT administrator doesn’t have enough backup restore or repairing the active directory is highly impossible.
Before restore proper information to be made and rebooted the domino server and selected advance boot option and select the restore options. And select the proper and good backup and restore it. After restoring the backup domain server started and domain active directory should work proper.
As experience better to reinstall domain server and active directory is good practice.