On the path from LCS 2005 to Lync 2010, something went wrong...

Disclaimer: you cannot migrate from LCS 2005 to Lync 2010 directly. To do this, you must first migrate from LCS to OCS 2007 (R1 or R2) and then from OCS 2007 (R1 or R2) to Lync.

I had a problem the other day about a migration from LCS 2005.

The scenario was the following: an LCS environment was to be migrated to OCS 2007 R2 and then to Lync. The migration was done according to https://technet.microsoft.com/en-us/library/dd819973(office.13).aspx, but during the global settings move (https://technet.microsoft.com/en-us/library/dd819962(office.13).aspx) something went wrong: KB 911996 was not correctly installed (not all files were updated) and when the RTC Service object was deleted from the CN=Schema,DC=domain,DC=com, LCS couldn't start anymore and the migration was compromised.

In this situation, there are 3 things to take into consideration:

1. You don't really need to move the RTC objects from Schema to Configuration: this change was done in OCS in order to improve performance. Lync doesn't use AD that much (most of the data will be in SQL), so if you don't have a pressing business need to move the RTC objects to the Configuration partition, don't do it!

2. If you decide to move the objects, verify that KB 911996 is correctly installed. Check that all the files mentioned in the KB were updated before moving anything.

3. If the move went wrong, unless you re-install LCS or restore the AD, there isn't much you can do to get LCS running again.

Ok, so you're in the situation 3 and decided to skip the migration and install Lync directly. I have still to check if the user's contacts can be recovered (and will update this post once I tried it). If you don't care about the contacts (although you should), here's how you can move directly to Lync (this is not a supported migration path, but rather a fresh Lync install after a disaster).

0. Back up your AD (in case anything goes wrong - the next step in this is not supported by Microsoft, so if anything goes wrong, you're probably on your own).

1. Delete the RTC Service objects from AD.

2. Install Lync normally, as if it was a fresh install.

3. After the Lync install is finished (and you've tested the functionality with some new test users), you're ready to activate the users for Lync. You won't be able to do it from the Lync console, although you will be able to see them in the console as legacy users.

4. To activate a user for Lync, you must first remove all the information regarding the old server. You can do this by running in the Lync Powershell console Disable-CsUser "User Name". You must have rights for editing the AD user properties in order to do this operation.

5. After the user has been disabled, it can be acticvated for Lync as if he/she was a new user.

6. You must deploy the Lync 2010 client! Communicator 2005 will probably not work with Lync.