Cluster Ready Services
As mentioned earlier in this chapter, CRS should be installed in its own home directory called
CRS_HOME. As part of the CRS installation, you will have to configure two particular locations
that are not specific to any instance but are used by the cluster itself: the Oracle Cluster Registry
and the voting disk. The Oracle Cluster Registry (OCR) is the location where the cluster stores its
metadata, and 256MB is the minimum amount of disk space required to hold the cluster metadata.
The voting disk is used by the cluster to resolve situations where one or more nodes in the cluster
lose contact with other nodes in the cluster over the private interconnect. In this way, you have a
way to shut off one node or one group of nodes from writing to the shared disk files because it
assumes it is in control of the shared storage. As with the OCR disk, the voting disk requires a
minimum of 256MB of free disk space on the device.
The locations of the OCR disk and the voting disk must be on separate raw devices, even
when you are using ASM for your other database files; however, if you are using OCFS, the OCR
disk and the voting disk can exist as files on an OCFS volume. In the examples that follow, I will
use raw devices for the OCR and voting disks; this is the Oracle-recommended method.
As of Oracle Database 10g Release 2, the runcluvfy.sh command verifies that the server
memory, user equivalence, network interfaces, required packages, and connectivity among the
nodes in the cluster are configured correctly for a CRS installation.
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