Oracle Local Registry (OLR) in RAC

In 11gR2, addition to OCR, we have another component called OLR installed on each node in the cluster. It is a local registry for node specific purposes. The OLR is not shared by other nodes in the cluster. It is installed and configured when clusterware is installed.

Why OLR is used and why was it introduced.

In 10g, we cannot store OCR’s in ASM and hence to startup the clusterware, oracle uses OCR but what happens when OCR is stored is ASM in 11g.

OCR should be accessible to find out the resources that need to be started or not. But, if OCR is on ASM, it can’t read until ASM (which itself is the resource of the node and this information is stored in OCR) is up.

 To answer this, Oracle introduced a component called OLR.

Ø  It is the first file used to startup the clusterware when OCR is stored on ASM.

Ø  Information about the resources that needs to be started on a node is stored in an OS file called ORACLE LOCAL REGISTRY (OLR).

Ø  Since OLR is an OS file, it can be accessed by various processes on the node for read/write irrespective of the status of cluster (up/down).

Ø  When a node joins the cluster, OLR on that node is read, various resources, including ASM are started on the node.

Ø  Once ASM is up, OCR is accessible and is used henceforth to manage all the cluster nodes. If OLR is missing or corrupted, clusterware can’t be started on that node.

Where is OLR located

It is located $GRID_HOME/cdata/<hostname>.olr .  The location of OLR is stored in /etc/oracle/olr.loc and used by OHASD.

What does OLR contain

The OLR stores

·         Clusterware version info.

·         Clusterware configuration

·         Configuration of various resources which needs to be started on the node,etc.

To see the contents in the OLR file, we can use following commands and see the resources.

[root@rac1 ~]# ocrconfig -local -manualbackup

host01     2014/03/16 01:20:27     /u01/app/grid/11.2.0.3/product/grid_1/cdata/rac1/backup_20140316_012027.olr

[root@rac1 ~]# strings /u01/app/grid/11.2.0.3/product/grid_1/cdata/rac1/backup_20140316_012027.olr |grep -v type |grep ora!

ora!drivers!acfs

ora!crsd

ora!asm

ora!evmd

ora!ctssd

ora!cssd

ora!cssdmonitor

ora!diskmon

ora!gpnpd

ora!gipcd

ora!mdnsd

OLR administration

Checking the status of the OLR file on each node.

$ ocrcheck –local

OCRDUMP is used to dump the contents of the OLR to text terminal

$ocrdump –local –stdout

We can export and import  the OLR file using OCRCONFIG

$ocrconfig –local –export  <export file name>

$ocrconfig –local –import  <file_name>

We can even the repair the OLR file if it corrupted.

$ocrconfig –local –repair –olr <filename>

OLR is backed up at the end of the installation or an upgrade. After that time we need to manually backup the OLR. Automatic backups are not supported for OLR.

$ocrconfig –local –manualbackup.

Viewing the contents of backup file

$ocrdump  -local –backupfile <olr_backup_file_name>

To change the OLR backup location

$ocrconfig –local –backuploc  <new_backup_location>

To restore OLR

$crsctl stop crs

$ocrconfig –local –restore_file_name

$ocrcheck –local

$crsctl start crs

$cluvfy comp olr   -- to check the integrity of the OLR file which was restored.