Something I have had to do on a regular enough basis to want to post about but irregular enough that I don’t remember…
So here it is.

1. Log onto OCS server and ensure that all users have been migrated
2. Ensure all Conference Directories are empty and have been migrated to Lync
3. From the Lync server – Use the Get-CsConferenceDirectory command in the Lync Management Shell to find the conference directory on the pool you want to remove. There will be a number in the Identity field, and that’s what you need for the next command.
4. Use the Remove-CsConferenceDirectory -Identity (number from step 3 result) -Force command. If you don’t use the force parameter, it will give you an error if the directory isn’t empty. You will be prompted to confirm your choice whether you use Force or not. Simply enter a Y or A to finish executing the command.
5. Stop all OCS Services
6. Deactivate Server Roles
   These server roles should be deactivated in the following sequence:
• A/V Conferencing ServerA/V Conferencing Server
• Web Conferencing Server
• Web Components Server
• Front End Server
7. Uninstall the OCS Components, be sure to uninstall all the non-essential bits first. Rule of thumb – do the bits that don’t warn first. Followed by the rest (Exclude the API stuff until last!)
8. Verify that All OCS component are removed
9. Log on to Lync, run Topology builder and then remove the BackCompat Site