Exchange 2013 copy queue length problem

I have an Exchange 2013 three node DAG. The servers are Mail 1, Mail 2 and Mail 3. We have several databases on Mail 1 and two are on Mail 3. Mail 2 is reporting a copy queue length of 400 and it is growing for the databases that are on Mail 3.

Does this indicate that the problem is on Mail 2 or Mail 3?  What causes a copy queue length?
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Adam FarageEnterprise ArchCommented:
You have two queues, copy queue and replay queue...

The copy queue is basically the number of logs that need to be shipped from the active copy to the passive, and the replay queue is the number of logs that are awaiting replay into the passive copy.

If you are having issues with a passive copies copy queue length, this means that there is an issue with log shipment between the Active copy and the Passive copy. This could be the MAPI / Replication network (e.g: networking issues), IPv6 being disabled or something else that is stopping the Active copy from replaying to the Passive copy.

In this situation I would try the following:

- Run Test-ReplicationHealth against the server in which the active and passive copies are hosted on:

Test-ReplicationHealth -Identity ActiveMailboxServer | FL

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Test-ReplicationHealth -Identity PassiveMailboxServer | FL

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- Review the Event Viewer: Application logs for replication issues between the two servers
- Look at the network layer to ensure that communication is up on the enabled REPLICATION network. You can find out which network is which by running the following:

Get-DatabaseAvailabilityGroupNetwork | FL

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From here, look to make sure that replication is enabled on one of the two (or if a single network, make sure replication is enabled) and that the two nodes can communicate.

- Check AV on the local servers, along with firewall rules and the switches themselves for any errors.

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wayy2beAuthor Commented:
So would the problem be the passive copy on Mail 2. All the test check out ok.
Adam FarageEnterprise ArchCommented:
Run the following:

Get-MailboxDatabaseCopyStatus | FL 

Open in new window

Post it here..
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wayy2beAuthor Commented:
Now we are seeing these errors from parent domain to child domain:

The call to Microsoft Exchange Active Directory Topology Service on server 'Topology ClientTcpEndpoint(localhost)' returned an error. No suitable domain controller was found in doamin ''

This error wqas received from a CAS server in the parent domain. The domain the error references is the child domain.

What can cause this?
Adam FarageEnterprise ArchCommented:
I would check that the AD Sites and Services is set properly, and that domain controllers and a global catalog server are local to the site in which Exchange is located. Remember: the site and domain in which exchange resides in requires at least one domain controller and one global catalog server.

If this is fine, then two other things I would check:

- make sure audit logging and security logging permissions are set for the Exchange Servers AD Security Group (
- Make sure that you did not disable IPv6 on accident
wayy2beAuthor Commented:
What is best practice for Exchange Windows updates?  Do you have a Microsoft cited reference that I can show to our team?
Adam FarageEnterprise ArchCommented:
Nothing. Just test them first, and then if all works well install them into production.
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