If you had placed the server into maintenance mode then you can run the commands or the script for stopping maintenance mode after the installation is finished (refer to the notes above).From the location that you extracted the cumulative update files run In this article I will demonstrate the step by step process for installing cumulative updates and service packs for Exchange Server 2013.The steps for installing cumulative updates and service packs on Exchange 2013 are: If you have multi-role CAS/MBX servers installed then setup updates the roles in the correct order anyway, and you should simply start with the internet-facing servers.When setup is complete you will be prompted to restart the server if required.After deploying an Exchange 2013 cumulative update there are a number of post-installation tasks that may be required.Some cumulative updates will include Active Directory schema changes.

You will need to accept the license agreement each time you upgrade a server. If any pre-requisites are not met setup will stop and warn you about them, otherwise you will be able to proceed with the upgrade.

Note: The AD preparation tasks are not required to be run separately to the upgrade of Exchange, unless in circumstances where you need to separate the tasks to different teams with different permissions, or if you have a multi-domain forest and want to control the AD changes.

Before applying the schema update follow the steps provided by Michael B Smith to retrieve the existing Exchange schema version, so that you can compare it before and after the AD preparation steps have been completed to verify that the schema update was applied.

In other words, you should plan to update all DAG members within a short period of time, and not allow them to run at different versions for days, weeks or months.

Mailbox servers in a multi-server environment, whether installed as standalone or as a multi-role server, should be placed into maintenance mode before installing the cumulative update.