Installing Exchange 2007 or 2010 in to a mixed organization will create a valid PDN entry and break OAB Generation

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New PDN's are really bad and will they will break the OAB Generation process. For most of the fixes you can follow my other blog found here: [https://blogs.msdn.com/dgoldman/archive/2005/11/18/OAB-PDN-Changes-and-Exchange-Site-Consolidations.aspx] which describes PDN's in great detail. For all 9340 PDN issues you can use OABInteg to scan the log for the legacyExchangeDN found in the 9340 event id, and then get it removed if they are invalid and this will fix the generation's compare process.

Now when you install Exchange 2007 or Exchange 2010 to create a mixed organization we will create a new container PDN of '/o=ORG/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients'. When you create a new mail enabled object the new object will be stamped with this legacyExchangeDN if it is an Exchange 2007 object. If you are building all (3) three versions of the OAB (OAB Version 2, OAB Version 3 and OAB Version 4) this will cause a PDN issue. OAB Version 2 and OAB Version 3 will still be affected by PDN issues thus breaking the OAB download for them until this is fixed.

NOTE: OAB Version 4  is not affected by PDN strings due to the fact we changed the way OAB Version 4 is generated. To fix this issue you will have to follow the steps in this blog (1) one time to merge this string.

The only way to get this added to the OAB (if you are generating OAB Version 2 and OAB Version 3 and are on Exchange 2003 Service Pack 2) is to add the following registry key 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeSA\Parameters\OAL post full if diff fails'. This will cause a full download for legacy OAB clients (OAB Version 2 and OAB Version 3 clients) as they need to reconstruct the pdndex.oab file when they do the full download. OAB Version 4 is built differently and users already downloading OAB Version 4 will *not* need to do a full download.

By adding this registry key you will allow the OAB Generation process to merge this new string in to the OAB PDN table and this will take care of the problem. Once this has been done the key *MUST* be removed, otherwise every time you have a PDN failure we will post a new OAB and cause OAB full downloads for legacy clients.

Event Type:           Warning
Event Source:        MSExchangeSA
Event Category:    OAL Generator
Event ID:               9340
Date:                     8/10/2007
Time:                     5:06:20 AM
User:                     N/A
Computer:             OAB-Gen-Server
Description:
A new parent Legacy Exchange DN container value '/o=ORG/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Recipients' was found during generation of the differential update file for offline address list '\Global Address List'.  This will force clients using this offline address list to do a full download of the offline address list.

- Default Offline Address List

For more information, click https://www.microsoft.com/contentredirect.asp.

Event Type:           Warning
Event Source:        MSExchangeSA
Event Category:    OAL Generator
Event ID:               9360
Date:                     8/10/2007
Time:                     5:06:20 AM
User:                     N/A
Computer:             OAB-Gen-Server
Description:

OALGen encountered an error while generating the changes.oab file for version 2 and 3 differential downloads of address list '\Global Address List'.  The offline address list has not been updated so clients will not be able to download the current set of changes.  Check other logged events to find the cause of this error.

If the cause of the problem was intentional or cannot be resolved, OALGen can be forced to post a full offline address list by creating the DWORD registry key 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeSA\Parameters\OAL post full if diff fails' and setting it to 1 on this server.  When OALGen next generates the offline address list, clients will perform a full OAB download.  After that time, the registry key should be removed to prevent further full downloads.

- Default Offline Address List

How to fix (Merging in new PDN)
1. Turn up logging: https://blogs.msdn.com/dgoldman/archive/2006/08/26/725860.aspx
2. Build your Offline Address Book.
3. Look for the 9340 and 9360 event id for the following legacyExchangeDN ' '
4. open up Regedit
5. Navigate to the following registry key 'HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeSA\Parameters\
6. Add a new DWORD Value 'OAL Post Full If Diff fails'
7. Set the value to 1
8. Rebuild your Offline Address Book and look for the 9107 event. Make sure you did not get a 9340 and 9360 event
9. Remove the registry key and you are done!
10. Turn down logging: https://blogs.msdn.com/dgoldman/archive/2006/08/26/725860.aspx

Dave