You can use System Manager to update a cluster or individual nodes in HA pairs.
More information
Updating the cluster nondisruptively
You can use System Manager to update a cluster or individual nodes in HA pairs that are running Data ONTAP 8.3.1 to a specific version of ONTAP software without disrupting access to client data.
How you update a cluster nondisruptively
You can use System Manager to update a cluster nondisruptively to a specific Data ONTAP version. In a nondisruptive update, you have to select a Data ONTAP image, validate that your cluster is ready for the update, and then perform the update.
Cluster Update window
You can use the Cluster Update window to perform an automated cluster upgrade without disrupting access to client data.