Updating your Active Directory Schema is something that needs to be done from time to time whether we like it or not. It is done to either support a new version of the OS Domain controller or because an AD integrated application such as Exchange, Skype for Business or SCCM requires the update. Regardless of the reasons the mere mention of an Active Directory ( AD) Schema update would make administrators cringe. The dreaded fear of the schema update is mostly due to the fact that this an update that cannot be undone. There is no uninstall button that allows you to reverse your changes. Things would get complicated if you have AD-integrated applications or have third party applications that also extended your schema.
Active Directory is like a beating heart
For those not sure what Active Directory is, it is a database of objects that represents users, computers, groups etc in your network, as well as being used for authentication and authorization. The schema is the component of Active Directory that defines all the objects with classes and attributes. For each version of Windows Server Domain Services, for instance the schema is different between AD 2003 and AD 2008 and AD 20012. When you introduce a new Domain controller with newer version OS you will need to update your schema.
I sometimes refer to AD as the heart of the network. The flow of the network, your enterprise objects, pass through this beating heart and if it has a brief hiccup or is slowed down it can affect the overall function of your network. Users not being able to login to their computers can have major impacts to the business and productivity loss can cost lost dollars. A non-working heart can be almost paralyzing for some businesses.
Upgrade all things NOW!
If there is mention of a schema update most would tend to delay an upgrade until they felt it was “safe”. Now this push of new product releases every 18 -24 months by Microsoft, it has introduced a re-thinking of sorts. In effort to reduce the fear and increase upgrades they have made these schema updates a little less painful and sometimes almost transparent. With each new release they simplify and make it easier to deploy and update.
With Windows server 2012 they made that process simpler by simplifying the upgrade process. The functions of with adprep and /forestprep, /domainprep have now been wrapped up into the Active Directory Domain Services role installation process making the process much easier through a few click of next. You can still use the command and do it manually if you want to be old school.
Schema updates are almost required for every Exchange Service Pack or major CU update now. The same can be said for other Microsoft applications such as Skype for Business and SCCM. They have made it so easy that in some cases, by installing the Application update such as a CU for Exchange 2013 the schema update process was built into the application. Given that the account you were using to run the Exchange update had all the appropriate permissions to update AD the schema, the update would be easy and seamless.
I think the level of fear of schema updates has decreased somewhat in past several years with administrators having to do it more often and the process to update keeps getting easier by Microsoft. Now if you have third party applications that extend your schema that may not be as pain free. As with any upgrade/update, you should always plan accordingly and test as much as possible, even the simple point and click ones.