Oracle Clusterware uses voting files to provide fencing and cluster node membership determination. OCR provides cluster configuration information. You can place the Oracle Clusterware files on either Oracle ASM or on shared common disk storage. If you configure Oracle Clusterware on storage that does not provide file redundancy, then Oracle recommends that you configure multiple locations for OCR and voting files. The voting files and OCR are described as follows:
Voting Files
Oracle Clusterware uses voting files to determine which nodes are members of a cluster. You can configure voting files on Oracle ASM, or you can configure voting files on shared storage.
If you configure voting files on Oracle ASM, then you do not need to manually configure the voting files. Depending on the redundancy of your disk group, an appropriate number of voting files are created.
If you do not configure voting files on Oracle ASM, then for high availability, Oracle recommends that you have a minimum of three voting files on physically separate storage. This avoids having a single point of failure. If you configure a single voting file, then you must use external mirroring to provide redundancy.
Oracle recommends that you do not use more than five voting files, even though Oracle supports a maximum number of 15 voting files.
Oracle Clusterware uses the Oracle Cluster Registry (OCR) to store and manage information about the components that Oracle Clusterware controls, such as Oracle RAC databases, listeners, virtual IP addresses (VIPs), and services and any applications. OCR stores configuration information in a series of key-value pairs in a tree structure. To ensure cluster high availability, Oracle recommends that you define multiple OCR locations. In addition:
You can have up to five OCR locations
Each OCR ___location must reside on shared storage that is accessible by all of the nodes in the cluster
You can replace a failed OCR ___location online if it is not the only OCR ___location
You must update OCR through supported utilities such as Oracle Enterprise Manager, the Oracle Clusterware Control Utility (CRSCTL), the Server Control Utility (SRVCTL), the OCR configuration utility (OCRCONFIG), or the Database Configuration Assistant (DBCA)
See Also:
Administering Oracle Clusterware for more information about voting files and OCR