For any technical or non-technical reason, you may want to downgrade a successful or failed upgrade of Oracle Clusterware 11g R2 to the previous version as it was before 11g R2. In order to do so, you will need to complete the following downgrade procedure:
$GRID_HOME/crs/installdirectory and execute the
rootcrs.pl -downgradescript on all nodes in a cluster. This script will stop the resources and shut down the cluster stack on the node.
/u01/app/11.2.0/grid/crs/install/rootcrs.pl downgrade [-force]
-forceflag to stop partial or failed 11g R2 upgrades. However, this command neither resets the OCR nor deletes
rootcrs.pl -downgradescript is ...