To run Oracle RAC in configurations with different versions of Oracle Database in the same cluster, you must first install Oracle Grid Infrastructure, which must be the same version, or higher, as the highest version of Oracle Database that you want to deploy in this cluster. For example, to run an Oracle RAC 11g release 2 (11.2) database and an Oracle RAC 12c database in the same cluster, you must install Oracle Grid Infrastructure 12c. Contact My Oracle Support for more information about version compatibility in Oracle RAC environments.
Note:
Oracle does not support deploying an Oracle9i cluster in an Oracle Grid Infrastructure 12c environment.