OLR (Oracle Local Registry) in RAC 11gR2

Oracle Clusterware 11g Release 2 an additional component related to the OCR called the Oracle Local Registry (OLR) is installed on each node in the cluster. The OLR is a local registry for node specific resources. 

In Oracle Clusterware 11g Release 2, each node in a cluster has a local registry for node specific resources, called an Oracle Local Registry (OLR), which is installed and configured when Oracle Clusterware installs OCR.

It is the very first file that is accessed to startup  clusterware when OCR is stored on ASM. OCR should be accessible to find out the resources which need to be started on a node. If OCR is on ASM, it can’t be read until ASM (which itself is a resource for the node and this information is stored in OCR) is up. To resolve this problem, information about the resources which need to be started on a node is stored in an operating system  file which is called Oracle Local Registry or OLR. Since OLR is a file an operating system file, it can be accessed by various processes on the node for read/write irrespective of the status of the clusterware (up/down). Hence, when  a node joins the cluster,  OLR on that node is read, various resources ,including ASM  are started on the node  . Once ASM is up , OCR is accessible.

By default, OLR is located at $GRID_HOME/cdata/hostname.olr.

The OLR contains the information about ORA_CRS_HOME, localhost version, active version, GPnP details, OCR latest backup time and location, information about OCR daily, weekly backup location
and node name etc.

You can manage the OLR by using the ocrcheck, ocrdump, and ocrconfig utilities with the -local option.

To see the location of the OLR, use the ocrcheck utility:
$ ocrcheck -config -local

You can check the status of the OLR as follows:
# ocrcheck -local

You can display the content of OLR to the text terminal that initiated the program using the OCRDUMP utility, as follows:
$ ocrdump -local -stdout

You can perform administrative tasks on OLR using the OCRCONFIG utility. To export OLR to a file:
# ocrconfig –local –export file_name

To import a specified file to OLR:
# ocrconfig –local –import file_name


To modify the OLR file on the local node:
# ocrconfig –local –repair olr file_name

Note: The olr keyword used with the -repair option is valid only when -local is used.