The Oracle Cluster Registry and the Voting Disk

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There are two storage locations of Oracle RAC. They are the Oracle Cluster Registry and the Voting Disk.

Oracle RAC uses two storage locations, which can be accessed by all cluster members:

The Oracle Cluster Registry (OCR)
Contains information for managing the cluster
The Voting Disk
Contains information to determine which nodes are active members of the cluster at any given moment

In Oracle RAC 10g Release 2, these storage locations can be files in a shared file format such as OCFS2, or they can be Linux® configured raw storage or block Linux devices. A block device in Linux is an unformatted partitioned disk that might be named, for example, /dev/dasda1, and shared by bringing the device online on all of the nodes in the cluster. It is not necessary for either the OCR or Voting Disk to be full disks.

Although block devices are not configured as raw storage, Oracle has direct access and uses them as raw storage.

Devices configured in Linux as raw devices are being deprecated, but depending on the Linux distribution they might be used in Oracle RAC 10.2.0.2 and 10.2.0.3. In the case of using raw devices for later versions, consult Oracle documentation for instructions.

The following instructions help to prepare block devices for use as OCR and Voting Disk and backups. After these components are set up, when clusterware is installed nothing more must be done with them by the administrator, unless the devices must be replaced for some reason.

Each OCR or Voting Disk and each back-up must have 100 MB of storage available.

  1. Create a partition table for the DASD by issuing this command:
    fsdasd -a /dev/dasdn
  2. Clear the residual data with the following command:
    dd  if=/dev/zero of=/dev/dasdn1 bs=1M count=2347
  3. Change the disk owner to the user oracle for the Voting Disk and back ups.
  4. For all the disks, change the group to oinstall.
  5. For all the disks, set the MODE to 0660.
    Note: After the installation, the owner of OCR is to the user oracle automatically.
  6. In Linux SLES 10 SP2, create a file in /etc/udev/rules.d named 98-oracle.permissions.rules with these lines:
    # for partitions import parent information
KERNEL=="*[0-9]", IMPORT{parent}=="ID_*"
# OCR disks
KERNEL=="dasdf1", OWNER="root", GROUP="oinstall" MODE="0660"
KERNEL=="dasdp1", OWNER="root", GROUP="oinstall" MODE="0660"
# VOTING DISKS
KERNEL=="dasdg1", OWNER="oracle", GROUP="oinstall" MODE="0660"
KERNEL=="dasdq1", OWNER="oracle", GROUP="oinstall" MODE="0660"

This file shows two block devices for OCR and a back-up, and two more for Voting Disks.

IMPORTANT

It is highly recommended to maintain cluster-wide persistent disk device names. For details, see Setting up persistent names for disk devices.