Exchange Updates installing slow on Windows Server 2012 R2

For customers who are running Exchange on Windows Server 2012 R2, we want to make certain you are aware of a condition which can substantially increase the amount of time it takes to install Exchange Updates on this OS. Working with the .Net team, we have discovered that systems which have applied Windows Update KB3097966 can take 50% more time to install Exchange. The .Net team is working on a resolution to this and will include a fix in a future product update. In the meantime, customers who have deployed this Windows update can take a one-time action on their server before installing Exchange or a Cumulative Update to bring installation time back to normal. This procedure needs to be done once on every Exchange server running Windows Server 2012 R2. The command to execute is:

“%windir%\Microsoft.NET\Framework64\v4.0.30319\ngen.exe update”

Errors and warnings encountered running this command can be safely ignored provided the final exit status code of 0 is reported in the output.