XADM: Slow Intra-site Directory Replication Between Servers (152942)

SYMPTOMS

Microsoft Exchange Server computers, version 4.0, with Microsoft Exchange Service Pack 2 (SP2) loaded might indicate that replication is occurring (through Performance Monitor and Event Viewer logging), but replication never completes or catches up between one or more Microsoft Exchange Servers within the same Microsoft Exchange Site. You might notice this by not seeing mailboxes, custom recipients, other objects, or modifications to objects appear in one or more Microsoft Exchange Server Directories.

CAUSE

When a target Microsoft Exchange Server computer is busy replicating with other Microsoft Exchange Server computers, it might not return its UUID when it refuses a connection from a requesting Microsoft Exchange Server. This results in the requesting Server incorrectly assigning the wrong UUID to the "Reps-From" field for the target Server. The next time the requesting Server attempts replication with the target Server, it "sees" a different UUID on the target Server, considers it a "new" Server, and attempts to replicate all objects. This can occur repeatedly if the requesting Server is refused the connection again at a later time.

STATUS

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 4.0. This problem was corrected in the latest Microsoft Exchange Service Pack. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

WORKAROUND

One possible workaround is to increase the following registry value on all Microsoft Exchange Servers within the Microsoft Exchange Site to a number equal to or greater than the total number of Servers in the Site. Note that modifying this value requires adequate RAM memory resources on all the computers on which the modification is made. The default for this value is 10 (0xA).

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeDS
                     \Parameters\Replicator maximum concurrent read threads

WARNING: If this setting is changed, and adequate resources do not exist on the server, several detrimental side effects may result including: mail flow failure; and/or Directory, Information Store, or MTA operational intermittency or failure.

MORE INFORMATION

It is important to confirm that the problem documented here is indeed the issue BEFORE proceeding with corrective actions. To diagnose this issue, perform the following:

Determine the UUID for the Directory Synchronization Agent (DSA) on the Microsoft Exchange Server which is not sending out updates.

Start the Microsoft Exchange Administrator program in raw mode (Admin.exe /r) against the Microsoft Exchange Server.

Highlight the <sitename>. Configuration.Servers.<this-Server s- name>.Directory Service

Select, File, Raw Properties..., and Invocation-ID. Note the first and last 4 characters listed in the Edit Value string. This is the UUID.
Compare the above UUID with the replication UUID listed on one of the Microsoft Exchange Servers that has not received the replicas yet.

Start the Microsoft Exchange Administrator program in raw mode against the non-replicated Microsoft Exchange Server.

Highlight, <sitename>.

Select File, Raw Properties...,Reps-From.

In the Attributes Value scroll box, move the horizontal scroll bar to the far right until the Microsoft Exchange Server names can be seen. Scroll through the list until the servername in step 1 is found.

Double click on this entry and view Replica link.

The value in the UUID: field should be the same UUID noted in step 1. If it is not, this indicates the condition documented in this article. If the UUIDs match, the problem is not a result of this issue and implementing the hotfix or workaround is not recommended.