Starting with Oracle Grid Infrastructure 12c Release 2 (12.2), you must use Oracle Automatic Storage Management (Oracle ASM) to store voting files and OCR files.

For new installations, use Oracle Automatic Storage Management (Oracle ASM) to store voting files and OCR files. If you are installing on IBM POWER, and you want to use a cluster file system, then you must use the IBM General Parallel File System (GPFS).

If your database files are stored on a shared file system, then you can continue to use the same for database files, instead of moving them to Oracle ASM storage.