How to Specify the Location of Data Files on a Shared File System
When dbca prompts you for a storage option, select Cluster File
When dbca prompts you for the location, select the option for common
After selecting the option for a common location, type the name of the directory on the shared
file system and press Return.
After you have created the Oracle database, go to Configuring
Resources for Support for Oracle RAC Database Instances.