Simplified process:
1) Copy the Exchange 2010 SP3 media to the hard drive of your Exchange server(s)
2) Right click the setup.exe and click ‘run-as-administrator’
3) Proceed through the upgrade process and reboot the server at the end
Note: I recommend upgrading servers one at a time.
More complex environments:
- If you are upgrading an Exchange 2010 DAG to SP3 you can follow these steps for installing Exchange Service Packs and Rollups on DAG Members.
- If you have servers with separate roles for example CAS servers and Mailbox servers and separate Exchange Servers, it is recommended that you upgrade the client access servers first.