Voting Disk and OCR

Voting disk –Manages cluster membership and arbitrates cluster ownership between the nodes in case of network failures. The voting disk is a file that resides on shared storage. For high availability, Oracle recommends that you have more than one voting disk, and that you have an odd number of voting disks. If you define a single voting disk, then use mirroring at the file system level for redundancy.

Oracle Cluster Registry (OCR)– Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR contains information such as which database instances run on which nodes and which services run on which databases. The OCR also stores information about processes that Oracle Clusterware controls. The OCR resides on shared storage that is accessible by all the nodes in your cluster. Oracle Clusterware can multiplex, or maintain multiple copies of, the OCR and Oracle recommends that you use this feature to ensure high availability.