One of the most arduous processes in DB maintenance is upgrading Databases across major versions, especially for complex RAC Clusters.
With the release of Database Plug-in (12.1.0.5.0), EM12c Rel 3 (12.1.0.3.0) now supports automated upgrading of RAC Clusters in addition to Standalone Databases.
Checkout Oracle’s Blog on EM12c https://blogs.oracle.com/oem/entry/automate_rac_cluster_upgrades_using