Downgrading Oracle Standalone Cluster

Use this procedure to downgrade Oracle Standalone Cluster after a successful upgrade.

1. As the grid user, delete the Oracle Grid Infrastructure 21c Management Database:

   %ORACLE_HOME%\bin\dbca -silent -deleteDatabase -sourceDB -MGMTDB

2. As the grid user, use the rootcrs.bat -downgrade command from 21c Grid home to downgrade Oracle Grid Infrastructure on all nodes, in any sequence. For example:

   %ORACLE_HOME%\crs\install\rootcrs.bat -downgrade

   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. As the grid user, downgrade the last node after you downgrade all other nodes:

   %ORACLE_HOME%\crs\install\rootcrs.bat -downgrade

4. Remove Oracle Grid Infrastructure 21c Grid home as the active Oracle Clusterware home:

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

   2. Use the following command to start the installer, where C:\app\21.0.0\grid is the location of the new (upgraded) Grid home:

      cd %ORACLE_HOME%\oui\bin
      setup.exe -nowait -waitforcompletion -ignoreSysPrereqs
      -updateNodeList -silent CRS=false
      ORACLE_HOME=C:\app\21.0.0\grid
      "CLUSTER_NODES=node1,node2,node3" 

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

5. Set previous release Grid home as the active Oracle Clusterware home:

   1. On any of the cluster member nodes where the rootupgrade.bat command 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 ORACLE_HOME is the location of the home directory from the earlier Oracle Clusterware installation:

      cd %ORACLE_HOME%\oui\bin 
      setup.exe -nowait -waitforcompletion -ignoreSysPrereqs 
      -updateNodeList -silent CRS=true 
      ORACLE_HOME=pre-upgrade-grid-home
      "CLUSTER_NODES=node1,node2,node3"

      pre-upgrade-grid-home is the previous release Grid home.

6. As the grid user, start the Oracle Clusterware stack on all nodes from previous release Grid home:

   crsctl start crs

7. As the grid user, remove the MGMTDB resource from previous Oracle Grid Infrastructure node:

   %ORACLE_HOME%\bin\srvctl remove mgmtdb -f

8. As the grid user, run DBCA in the silent mode from previous release Grid home and create the Management Database container database (CDB):

   %ORACLE_HOME%\bin\dbca -silent -createDatabase -createAsContainerDatabase true 
   -templateName MGMTSeed_Database.dbc -sid -MGMTDB -gdbName _mgmtdb 
   -storageType ASM -diskGroupName ASM_DG_NAME
   -datafileJarLocation template-data-file-location
   -characterset AL32UTF8 -autoGeneratePasswords -skipUserTemplateCheck

   template-data-file-location is the complete path of the template data file.

9. Configure the Management Database by running the Configuration Assistant from the %ORACLE_HOME%\bin\mgmtca.bat —local location.