Voting Disk and Oracle Cluster Registry

1.    Voting Disk: - Manages cluster membership by way of a health check and arbitrates cluster ownership among the instances in case of network failures. RAC uses the voting disk to determine which instances are members of a cluster. The voting disk must reside on shared disk. For high availability, Oracle recommends that you have multiple voting disks. The Oracle Clusterware enables multiple voting disks.

2. OCR File :- Cluster configuration information is maintained in Oracle Cluster Registry file. OCR relies on a distributed shared-cache architecture for optimizing queries against the cluster repository. Each node in the cluster maintains an in-memory copy of OCR, along with an OCR process that accesses its OCR cache.
When OCR client application needs to update the OCR, they communicate through their local OCR process to the OCR process that is performing input/output (I/O) for writing to the repository on disk.
The OCR client applications are Oracle Universal Installer (OUI), SRVCTL, Enterprise Manger (EM), Database Configuration Assistant (DBCA), Database Upgrade Assistant(DBUA), NetCA and Virtual Internet Protocol Configuration assistant (VIPCA). OCR also maintains dependency and status information for application resources defined within CRS, specifically databases, instances, services and node applications.

Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR also manages information about processes that Oracle Clusterware controls. The OCR stores configuration information in a series of key-value pairs within a directory tree structure. The OCR must reside on shared disk that is accessible by all of the nodes in your cluster. The Oracle Clusterware can multiplex the OCR and Oracle recommends that you use this feature to ensure cluster high availability.