NTDS ISAM: Database Corruption

There is a directory services event log that has been filling up with many errors in a day, and it keeps on repeating all over and over again. This network is fairly simple and the DC and 10 clients are there. Check out the below errors that I am getting:

Event Type: Information
Event Source: NTDS ISAM
Event Category: General
Event ID: 103
Date: 09/04/2005
Time: 10:07:09 AM
User: N/A
Computer: ACT1
Description:
NTDS (684) NTDSA: The database engine stopped the instance (0).



Event Type: Information
Event Source: NTDS ISAM
Event Category: General
Event ID: 102
Date: 09/04/2005
Time: 10:08:03 AM
User: N/A
Computer: ACT1
Description:
NTDS (696) NTDSA: The database engine started a new instance (0).


Event Type: Information
Event Source: NTDS General
Event Category: Service Control
Event ID: 1000
Date: 09/04/2005
Time: 10:08:25 AM
User: NT AUTHORITY\ANONYMOUS LOGON
Computer: ACT1
Description:
Microsoft Active Directory startup complete, version 5.2.3790.62



Event Type: Information
Event Source: NTDS General
Event Category: Service Control
Event ID: 1394
Date: 09/04/2005
Time: 10:08:55 AM
User: NT AUTHORITY\ANONYMOUS LOGON
Computer: ACT1
Description:
Attempts to update the Active Directory database are succeeding. The Net
Logon service has restarted.



Event Type: Error
Event Source: NTDS ISAM
Event Category: Database Corruption
Event ID: 467
Date: 09/04/2005
Time: 10:13:25 AM
User: N/A
Computer: ACT1
Description:
NTDS (696) NTDSA: Index DRA_USN_index of table datatable is corrupted (0).



Event Type: Warning
Event Source: NTDS KCC
Event Category: Knowledge Consistency Checker
Event ID: 1435
Date: 09/04/2005
Time: 10:13:25 AM
User: NT AUTHORITY\ANONYMOUS LOGON
Computer: ACT1
Description:
The Knowledge Consistency Checker (KCC) encountered an unexpected error
while performing an Active Directory operation.

Operation type:
KccModifyEntry
Object distinguished name:
CN=NTDS Site
Settings,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=Ourserver,DC=local

The operation will be retried at the next KCC interval.

Additional Data
Error value:
5 000020EF: SvcErr: DSID-02080495, problem 5012 (DIR_ERROR), data -1414

You can try to use the following procedures to perform offline defragmentation:

1. Change the garbage collection logging level to 1. Check the Directory Service event log for event ID 1646, which reports the amount of disk space that you can recover by performing offline defragmentation.
2. Back up system state. System state includes the database file and database log files as well as SYSVOL, NETLOGON, and the registry, among other things. Always ensure that a current backup exists prior to defragmenting database files.

For more methods go to this link here - http://technet.microsoft.com/library/Bb727061#EUAA

There are many reason that causes the NTDS database corruption. For example there could be hard disk failure because of bad sectors or disk write caching enabled on the disk. There could be unexpected shutdown of the server. If you have Antivirus installed then it could be scanning at Realtime for the NTDS database and transaction log files. For solving this issue, you will generally need to follow this link for troubleshooting - http://support.microsoft.com/?id=902396

The error that you are facing could occur if there is an issue with the hardware. But most of the times this error might not be related to hardware failure. It is possible that the database could be corrupted at the time of backup or because of some programs like antivirus software running on the server. So if you want to recover the corrupter Active Directory then you can follow the method given in this link.