DBCA fails to create 12.1.0.2 RAC database over 12.2 GI/ASM

When creating 12.1.0.2 RAC CDB on newly created 12.2.0.1 GI/ASM by using DBCA, the database creation failed with errors ORA-19504/.ORA-17502

By checking Oracle metalink, it is an Oracle bug (#21626377)  - RDBMS instance fails to identify the required disks to mount a disk group if compatible.asm of the diskgroup is higher than version of the software.

You can refer to the metalink note (Doc ID 21626377.8) for details. There are 2 ways to fix the issue:

1. Apply the BP 12.1.0.2.170418 (or later BPs) - 12.1.0.2.170718 (Jul 2017) Database Patch Set Update (DB PSU) - on Oracle 12.1.0.2 RDBMS home, so DBCA can create 12.1.0.2 database using the ASM diskgroup with compatible.asm set to 12.2.

2. Workaround 

- Create an ASM diskgroup with compatible.asm set to 12.1 and then try to create the 12.1 database.