Converting from Single-Instance Oracle Database to Oracle Real Application Clusters

You can convert from Oracle Database 12c Release 2 (12.2) single-instance databases to Oracle RAC using Oracle Database Configuration Assistant, rconfig, or Oracle Enterprise Manager.

For an in-place conversion, you cannot change the Oracle Home User. For an out-of-place conversion, you can change the Oracle Home User only if the Oracle home for the single-instance database is not already configured with a Windows Domain User Account.