After a successful or a failed upgrade, you can restore Oracle Clusterware to the previous release.
Downgrading Oracle Clusterware restores the Oracle Clusterware configuration to the state it was in before the Oracle Grid Infrastructure 18c upgrade. Any configuration changes you performed during or after the Oracle Grid Infrastructure 18c upgrade are removed and cannot be recovered.
To restore Oracle Clusterware to the previous release, use the downgrade procedure for the release to which you want to downgrade.
Starting with Oracle Grid Infrastructure 12c Release 2 (12.2), you can downgrade the cluster nodes in any sequence. You can downgrade all cluster nodes except one, in parallel. You must downgrade the last node after you downgrade all other nodes.
When downgrading after a failed upgrade, if the
rootcrs.batfile does not exist on a node, then instead of the executing the script use the command
perl rootcrs.pl. Use the Perl interpreter located in the Oracle Home directory.