Corrupted database the reason the index

Question

Hi there 
Due to sudden power outage I got my AD database corrupted, I am running DC on win server 2012 
and this is what contained in the log file 
Log Name:      Directory Service
Source:        NTDS ISAM
Date:          7/9/2014 4:12:01 PM
Event ID:      467
Task Category: Database Corruption
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      DC
Description:
NTDS (556) NTDSA: Database C:\Windows\NTDS\ntds.dit: Index INDEX_00020078 of table datatable is corrupted (0).
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="NTDS ISAM" />
    <EventID Qualifiers="0">467</EventID>
    <Level>2</Level>
    <Task>12</Task>
    <Keywords>0x80000000000000</Keywords>
    <TimeCreated SystemTime="2014-07-09T23:12:01.000000000Z" />
    <EventRecordID>3204</EventRecordID>
    <Channel>Directory Service</Channel>
    <Computer>DC.training.local</Computer>
    <Security />
  </System>
  <EventData>
    <Data>NTDS</Data>
    <Data>556</Data>
    <Data>NTDSA: </Data>
    <Data>INDEX_00020078</Data>
    <Data>datatable</Data>
    <Data>C:\Windows\NTDS\ntds.dit</Data>
    <Data>0</Data>
  </EventData>
</Event>

Answer 1

That is the index over the UsnChanged attribute - replication will stop working as this is used by the DRA to perform replications.
If you have other DCs in this domain, I would recommend to power off this machine and discard it and perform metadata cleanup on another DC:
http://support.microsoft.com/kb/216498/sv
To fix this issue you have to perform an offline defrag:
http://technet.microsoft.com/en-us/library/cc794920(v=ws.10).aspx
Enfo Zipper
Christoffer Andersson – Principal Advisor
http://blogs.chrisse.se - Directory Services Blog