If you have an existing Oracle Clusterware installation, then you upgrade your existing cluster by performing an out-of-place upgrade. You cannot perform an in-place upgrade.

The following topics list the steps you can perform before you upgrade Oracle Grid Infrastructure:

• Upgrade Checklist for Oracle Grid Infrastructure
  Review this checklist before upgrading an existing Oracle Grid Infrastructure. A cluster is being upgraded until all cluster member nodes are running the new installations, and the new clusterware becomes the active version.
• Tasks to Complete Before Upgrading Oracle Grid Infrastructure
  Review the tasks before upgrading Oracle Clusterware.
• Create an Oracle ASM Password File
  In certain situations, you must create an Oracle ASM password file before you can upgrade to Oracle Grid Infrastructure 19c.
• Running the Oracle ORAchk Upgrade Readiness Assessment
  Download and run the Oracle ORAchk Upgrade Readiness Assessment before upgrading Oracle Grid Infrastructure.
• Using CVU to Validate Readiness for Oracle Clusterware Upgrades
  Oracle recommends that you use Cluster Verification Utility (CVU) to help to ensure that your upgrade is successful.