How to check Active Directory replication

By | October 31, 2009

One of the questions asked most frequently by the system administrators is how to check the Active Directory replication or how to monitor the AD replication, most of the AD administrates know about the repadmin /showreps command however this command will provide the Last attempt status, like “Last attempt @ 2008-10-31 13:51:13 was successful” if any error while last attempt it will show the errors like the below one for communication issue

Last attempt @ 2009-04-18 01:45:51 failed, result 1722 (0x6ba):
The RPC server is unavailable.

Some time you will get the below status through repamin command

1. Active Directory replication has been preempted.
2. Replication posted, waiting.
3. Server busy

All the above status are related to replication progressing without any major issues, but we don’t know about the exact status

To get the exact status use the below procedure:

If the replication progressing (or) not ????

Let say am checking for test0000-test0005 (Connection object)
check the active directory replication on test0005

1. Run the “repadmin /showreps /v” on test0005
a. Check for respective connection object and partition (domain partition)
b. Check the USN value on /OU /PU
c. Find the below result

USNs: 215044188/OU, 0/PU
Last attempt @ 2008-10-31 15:05:20 was successful.

2. Check after some time if the value increase then the replication happening, as per the below screenshot replication happening because the USN: /OU value changing

(USNs: 221237525/OU, 0/PU
Last attempt @ 2008-10-31 15:05:20 was successful.

Now you see the change (USNs: 215044188/OU to USNs: 221237525/OU)

3. Also check other partition for the same server, for up to date USN, find the screenshot for configuration partition.

USNs: 262820263/OU, 262820263/PU
Last attempt @ 2008-10-31 15:05:20 was successful.

4. In order to complete the replication this USN /OU value should reach USNs: 262820263/OU

5. If this USN /OU value not changed for long time then replication failed (replication not progress) please check for event log for more info.

This procedures are mainly used to check The high-watermark value, it can help you deduce the state of progress on that replication link

USNs:. The high-watermark USN is the number that is followed by /OU.

The object update (OU) USN saves the position when in the middle of a replication cycle. It stays the same as the property update (PU) when replication is not occurring, and increases during a replication cycle. At the end of the cycle, the final USN replicated becomes the PU value and the OU is left to match. Thus, the OU indicates progress within a cycle, and the PU indicates the last update seen at the conclusion of a successful cycle. A PU of zero means that the link has never completed a successful cycle, as is the case when performing its first synchronization on a new domain controller connection. If the OU and PU are not equal, it means a replication cycle is in progress.

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