Use this procedure to downgrade to Oracle Grid Infrastructure 11g Release 2 (11.2) .

1. Delete the Oracle Grid Infrastructure 12c Release 2 (12.2) Management Database:

   dbca -silent -deleteDatabase -sourceDB -MGMTDB 

2. Use the command syntax Grid_home/crs/install/rootcrs.sh -downgrade to stop the Oracle Grid Infrastructure 12c Release 2 (12.2) resources, and to shut down the stack. Run this command from a directory that has write permissions for the Oracle Grid Infrastructure installation user.

   You can run the downgrade script in parallel on all cluster nodes, but one.

3. Downgrade the last node after you downgrade all other nodes:

   # /u01/app/12.2.0/grid/crs/install/rootcrs.sh -downgrade 

4. Follow these steps to remove Oracle Grid Infrastructure 12c Release 2 (12.2) Grid home as the active Oracle Clusterware home:

   1. On any of the cluster member nodes where the rootupgrade.sh script has run successfully, log in as the Oracle Grid Infrastructure installation owner.

   2. Use the following command to start the installer, where /u01/app/12.2.0/grid is the location of the new (upgraded) Grid home:

   $ cd /u01/app/12.2.0/grid/oui/bin 
   $ ./runInstaller -nowait -waitforcompletion -ignoreSysPrereqs -updateNodeList
    -silent CRS=false ORACLE_HOME=/u01/app/12.2.0/grid 
    "CLUSTER_NODES=node1,node2,node3" -doNotUpdateNodeList 
   

   Add the -cfs option if the Grid home is a shared home.

5. Follow these steps to set the Oracle Grid Infrastructure 11g Release 2 (11.2) Grid home as the active Oracle Clusterware home:

   1. On any of the cluster member nodes where the rootupgrade script has run successfully, log in as the Oracle Grid Infrastructure installation owner.

   2. Use the following command to start the installer, where the path you provide for the ORACLE_HOME is the location of the home directory from the earlier Oracle Clusterware installation.

      $ cd /u01/app/11.2.0/grid/oui/bin 
      $ ./runInstaller -nowait -waitforcompletion -ignoreSysPrereqs -updateNodeList
       -silent CRS=true ORACLE_HOME=/u01/app/11.2.0/grid 

      Add the -cfs option if the Grid home is a shared home.

6. Start the Oracle Clusterware stack manually from the earlier release Oracle Clusterware home using the command crsctl start crs. For example, where the earlier release home is /u01/app/11.2.0/grid, use the following command on each node:

   /u01/app/11.2.0/grid/bin/crsctl start crs