XADM: Directory Replication Conflicts and Event ID 1074 (195911)

SUMMARY

When you attempt to modify a Directory Object at the same time using multiple instances of the Exchange Server Administrator program on different servers in the same site, the user may receive the following Event in the Windows NT Application log:

   Event Id: 1074
   Source: MSExchangeDS
   Category: Replication
   Type: Warning
   Description:
   Replication warning: There was a conflict with replication.
   Modifications made to object
   /o=Alpha/ou=Omega/cn=Recipients/cn=Technical Disc by directory with
   globally unique identifier (GUID) 74799c39c5b2d11197230001fa6a0863
   EXCHANGE05 were lost.

This event indicates that a directory object was modified on two different servers in the same site before the change has had chance to be replicated. Because of this, one server's changes were discarded. Any directory object may be affected including a mailbox, distribution list, address-book view, or custom recipients.

You will not see the above Event ID in the log unless the Directory Service's diagnostic logging has been increased in the following diagnostics logging category: REPLICATION.

This is not a problem with the Microsoft Exchange Directory. The basic rule to follow when modifying objects is to make changes to an object from only one point in a site. If an object is modified on two different servers within the same site within the directory replication interval, then it is possible for directory replication conflicts to occur.

MORE INFORMATION

Microsoft Exchange Server uses the following methodology to handle conflicts during directory replication. The directory service first checks the Object-Version of the object when the directory service receives a change.

In most cases, the Object-Version is higher than the existing Object- Version of the object in the local directory, so the change will be committed to the local directory. If the Object-Version is lower, then the change is ignored and not committed to the local directory. If the Object- Version is the same value, then the directory service compares the existing DSA-Signature of the Object on the local directory to the incoming object's DSA-Signature. If these DSA-Signatures match, then the change is committed to the local directory. If the DSA-Signatures are different, then the Directory service compares the When-Changed attribute of the Object on the local directory and the When-Changed attribute of the incoming object change. The Directory service commits to the local directory the object that has the more recent When-Changed attribute.

The following are examples of activities that can lead to directory replication conflicts:

Exchange Administrators modifying any object from more than one server at the same time.
Running the Microsoft Mail migration from more than one server or workstation that is migrating msmail users to the same Exchange Server site. The conflicts will occur in this scenario if the msmail custom recipients are members of Exchange Server distribution lists that will be updated simultaneously by the computers performing the migration. In this scenario, the distribution lists' memberships may contain unknown objects that have gear icons associated with them. (Similar looking to Free Busy Agent Icon.)