Thursday, June 15, 2017

Oracle Local Registry [OLR]


Introduction:-

In Oracle Clusterware 11g release 2 (11.2), each node in a cluster has a local registry for node-specific resources, called an Oracle Local Registry (OLR), that is installed and configured when Oracle Clusterware installs OCR. OLR is local registry for node specific resources. OLR is not shared by other nodes in cluster. Multiple processes on each node have simultaneous read and write access to the OLR particular to the node on which they reside, regardless of whether Oracle Clusterware is running or fully functional.


Purpose Of OLR:-

It is the very first file that is accessed while starting clusterware when OCR is stored on ASM. OCR should be available to find out the resources which should be up 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 solve this issue, information about the resources which need to be started on a node is stored in an operating system  file which is called OLR. Since OLR is 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 and various resources including ASM are started on the node. Once ASM is up,OCR is accessible and is used henceforth to manage all the clusterware resources.If OLR is missing or corrupted, clusterware can’t be started on that node!


Details :-

With the OCR and Voting disks being placed in ASM, these files are accessible only when the cluster processes have started up and ASM instance is up and running. However without the OCR file the clusterware processes cannot start up. To resolve this, a copy of the Oracle Local Registry(OLR) registry is now created on each node during the initial installation which stores node specific information and allows us to get around the problem. OLR stores the information on the clusterware configuration, version information, and GpnP wallets. OHASD process mostly manages OLR. The OCR in turn is managed by the CRSD processes. The OLR is stored in GRID_HOME/cdata and must be available on the node before other services can be started up.Without this the clusterware will fail to start.


Location:-

The OLR location is stored in '/etc/oracle/olr.loc' or '/var/opt/oracle/olr.loc' depending on platform.


#The default location after installing Oracle Clusterware is:-

GI Cluster: <GI_HOME>/cdata/<hostname.olr>
GI Standalone (Oracle Restart): <GI_HOME>/cdata/localhost/<hostname.olr>

#To check the location using command (as oracle user):-
[oracle@rac1 ~]$ ocrcheck -local -config
Oracle Local Registry configuration is :
         Device/File Name         : /u01/app/11.2.0/grid/cdata/rac1.olr

#To check the location using command (as root user):-
[root@rac1 ~]# ocrcheck -local
Status of Oracle Local Registry is as follows :
         Version                  :          3
         Total space (kbytes)     :     262120
         Used space (kbytes)      :       2372
         Available space (kbytes) :     259748
         ID                       : 2017112488
         Device/File Name         : /u01/app/11.2.0/grid/cdata/rac1.olr
                                    Device/File integrity check succeeded

         Local registry integrity check succeeded

         Logical corruption check succeeded



What does OLR contain?

Information stored in the OLR is needed by OHASD to start or join a cluster.
The OLR stores data about :-
ORA_CRS_HOME
localhost version
active version
GPnP details
OCR latest backup time and location
information about OCR daily, weekly backup location
node name etc.


Commands :-


To display the content of OLR on the local node to the text terminal that initiated the program using the OCRDUMP utility
# ocrdump -local -stdout
# ocrdump -h

To export OLR to a file
# ocrconfig –local –export file_name

Note :-
Oracle recommends that you use the -manualbackup and -restore commands and not the -import and -export commands.When exporting OLR, Oracle recommends including "olr", the host name, and the timestamp in the name string. For example: olr_myhost1_20090603_0130_export

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

To manually back up OLR:(root)
# ocrconfig -local -manualbackup

Note:-
The OLR is backed up at the end of an installation or an upgrade. After that time, you can only manually back up the OLR. Automatic backups are not supported for the OLR. You should create a new backup when you migrate OCR from Oracle ASM to other storage, or when you migrate OCR from other storage to Oracle ASM. The default backup location for the OLR is in the path Grid_home/cdata/host_name.

To view the contents of the OLR backup file
#ocrdump -local -backupfile olr_backup_file_name

To change the OLR backup location
#ocrconfig -local -backuploc new_olr_backup_path

To List Available Backup
#ocrconfig -local -showbackup

Note:- 
Clusterware maintains the history of the five most recent manual backups and will not update/delete a manual backups after it has been created. Below command shows manual backups in the registry though they are removed or archived manually in OS file system by OS commands

[oracle@rac1 rac1]$ ocrconfig -local -showbackup

rac1    /u01/app/11.2.0/grid/cdata/rac1/backup_20170307_060226.olr
rac1    /u01/app/11.2.0/grid/cdata/rac1/backup_20170307_060225.olr
rac1    /u01/app/11.2.0/grid/cdata/rac1/backup_20170307_060222.olr
rac1    /u01/app/11.2.0/grid/cdata/rac1/backup_20170307_060220.olr
rac1    /u01/app/11.2.0/grid/cdata/rac1/backup_20170307_060218.olr

Here we can see list of 5 latest backups but physically we have only 3 latest backups available.
      
[oracle@rac1 rac1]$ ls -ltr
total 18964
-rw------- 1 root root 6447104 Mar  7 06:02 backup_20170307_060222.olr
-rw------- 1 root root 6467584 Mar  7 06:02 backup_20170307_060225.olr
-rw------- 1 root root 6467584 Mar  7 06:02 backup_20170307_060226.olr

Restoring OLR
We need to follow few steps to restore OLR, which have been described in my post "How To Restore OLR" Here .



References :-
https://docs.oracle.com/cd/E11882_01/rac.112/e41959/votocr.htm#CWADD837


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