Downgrade procedures for downgrading all Oracle Grid Infrastructure cluster types to 18c after successful or failed upgrade.

• Downgrading Oracle Standalone Cluster to 18c
  Use this procedure to downgrade Oracle Standalone Cluster to Oracle Grid Infrastructure 18c after a successful upgrade.
• Downgrading Oracle Domain Services Cluster to 18c
  Use this procedure to downgrade Oracle Domain Services Cluster to Oracle Grid Infrastructure 18c after a successful upgrade.
• Downgrading Oracle Member Cluster to 18c
  Use this procedure to downgrade Oracle Member Cluster to Oracle Grid Infrastructure 18c after a successful upgrade.
• Downgrading Oracle Grid Infrastructure to 18c when Upgrade Fails
  If upgrade of Oracle Grid Infrastructure fails before CVU post upgrade checks succeed, then you can run gridSetup.sh and downgrade Oracle Grid Infrastructure to the earlier release.