Oracle Local Registry (OLR) in RAC - 11gR2
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.
