Oracle Disk Manager architecture
When the ODM library is linked, Oracle is able to bypass all caching and locks at the file system layer and to communicate directly with raw volumes.
The SFCFS for Oracle RAC implementation of ODM generates performance equivalent to performance with raw devices while the storage uses easy-to-manage file systems.
All ODM features can operate in a cluster environment. Nodes communicate with each other before performing any operation that could potentially affect another node. For example, before creating a new data file with a specific name, ODM checks with other nodes to see if the file name is already in use.