OCR File and Voting Disk Administration by Example - (Oracle 10g)
OCR File and Voting Disk Administration by Example - (Oracle 10g)
by Jeff Hunter, Sr. Database Administrator
Contents
- Overview
- Example Configuration
- Administering the OCR File
View OCR Configuration Information
Add an OCR File
Relocate an OCR File
Repair an OCR File on a Local Node
Remove an OCR File - Backup the OCR File
Automatic OCR Backups
Manual OCR Exports
- Recover the OCR File
Recover OCR from Valid OCR Mirror
Recover OCR from Automatically Generated Physical Backup
Recover OCR from an OCR Export File
- Administering the Voting Disk
View Voting Disk Configuration Information
Add a Voting Disk
Remove a Voting Disk
Relocate a Voting Disk - Backup the Voting Disk
- Recover the Voting Disk
- Move the Voting Disk and OCR from OCFS to RAW Devices
Move the OCR
Move the Voting Disk - About the Author
Overview
Oracle Clusterware 10g, formerly known as Cluster Ready Services (CRS) is software that when installed on servers running the same operating system, enables the servers to be bound together to operate and function as a single server or cluster. This infrastructure simplifies the requirement for an Oracle Real Application Clusters (RAC) database by providing cluster software that is tightly integrated with the Oracle Database.
The Oracle Clusterware requires two critical clusterware components: a voting disk to record node membership information and the Oracle Cluster Registry (OCR) to record cluster configuration information:
Voting DiskOracle Cluster Registry (OCR)The voting disk is a shared partition that Oracle Clusterware uses to verify cluster node membership and status. Oracle Clusterware uses the voting disk to determine which instances are members of a cluster by way of a health check and arbitrates cluster ownership among the instances in case of network failures. The primary function of the voting disk is to manage node membership and prevent what is known as Split Brain Syndrome in which two or more instances attempt to control the RAC database. This can occur in cases where there is a break in communication between nodes through the interconnect.
The voting disk must reside on a shared disk(s) that is accessible by all of the nodes in the cluster. For high availability, Oracle recommends that you have multiple voting disks. Oracle Clusterware can be configured to maintain multiple voting disks (multiplexing) but you must have an odd number of voting disks, such as three, five, and so on. Oracle Clusterware supports a maximum of 32 voting disks. If you define a single voting disk, then you should use external mirroring to provide redundancy.
A node must be able to access more than half of the voting disks at any time. For example, if you have five voting disks configured, then a node must be able to access at least three of the voting disks at any time. If a node cannot access the minimum required number of voting disks it is evicted, or removed, from the cluster. After the cause of the failure has been corrected and access to the voting disks has been restored, you can instruct Oracle Clusterware to recover the failed node and restore it to the cluster.
Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. OCR is the repository of configuration information for the cluster that manages information about like the cluster node list and instance-to-node mapping information. This configuration information is used by many of the processes that make up the CRS as well as other cluster-aware applications which use this repository to share information amoung them. Some of the main components included in the OCR are:
- Node membership information
- Database instance, node, and other mapping information
- ASM (if configured)
- Application resource profiles such as VIP addresses, services, etc.
- Service characteristics
- Information about processes that Oracle Clusterware controls
- Information about any third-party applications controlled by CRS (10g R2 and later)
The OCR stores configuration information in a series of key-value pairs within a directory tree structure. To view the contents of the OCR in a human-readable format, run the ocrdump command. This will dump the contents of the OCR into an ASCII text file in the current directory named OCRDUMPFILE.
The OCR must reside on a shared disk(s) that is accessible by all of the nodes in the cluster. Oracle Clusterware 10g Release 2 allows you to multiplex the OCR and Oracle recommends that you use this feature to ensure cluster high availability. Oracle Clusterware allows for a maximum of two OCR locations; one is the primary and the second is an OCR mirror. If you define a single OCR, then you should use external mirroring to provide redundancy. You can replace a failed OCR online, and you can update the OCR through supported APIs such as Enterprise Manager, the Server Control Utility (SRVCTL), or the Database Configuration Assistant (DBCA).
This article provides a detailed look at how to administer the two critical Oracle Clusterware components — the voting disk and the Oracle Cluster Registry (OCR). The examples described in this guide were tested with Oracle RAC 10g Release 2 (10.2.0.4) on the Linux x86 platform.
It is highly recommended to take a backup of the voting disk and OCR file before making any changes! Instruction are included in this guide on how to perform backups of the voting disk and OCR file.
CRS_home The Oracle Clusterware binaries included in this article (i.e. crs_stat, ocrcheck, crsctl, etc.) are being executed from the Oracle Clusterware home directory which for the purpose of this article is /u01/app/crs. The environment variable $ORA_CRS_HOME is set for both the oracle and root user accounts to this directory and is also included in the $PATH:
[root@racnode1 ~]# echo $ORA_CRS_HOME /u01/app/crs [root@racnode1 ~]# which ocrcheck /u01/app/crs/bin/ocrcheck
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Example Configuration
The example configuration used in this article consists of a two-node RAC with a clustered database named racdb.idevelopment.info running Oracle RAC 10g Release 2 on the Linux x86 platform. The two node names are racnode1 and racnode2, each hosting a single Oracle instance named racdb1 and racdb2 respectively. For a detailed guide on building the example clustered database environment, please see:
Building an Inexpensive Oracle RAC 10 g Release 2 on Linux - (CentOS 5.3 / iSCSI)
The example Oracle Clusterware environment is configured with a single voting disk and a single OCR file on an OCFS2 clustered file system. Note that the voting disk is owned by the oracle user in the oinstall group with 0644 permissions while the OCR file is owned by root in the oinstall group with 0640 permissions:
Check Current OCR File
[oracle@racnode1 ~]$ ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4660 Available space (kbytes) : 257460 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded Device/File not configured Cluster registry integrity check succeededPreparation
[oracle@racnode1 ~]$ crsctl query css votedisk 0. 0 /u02/oradata/racdb/CSSFile located 1 votedisk(s).To prepare for the examples used in this guide, five new iSCSI volumes were created from the SAN and will be bound to RAW devices on all nodes in the RAC cluster. These five new volumes will be used to demonstrate how to move the current voting disk and OCR file from an OCFS2 file system to RAW devices:
Five New iSCSI Volumes and their Local Device Name Mappings iSCSI Target Name Local Device Name Disk Size iqn.2006-01.com.openfiler:racdb.ocr1 /dev/iscsi/ocr1/part 512 MB iqn.2006-01.com.openfiler:racdb.ocr2 /dev/iscsi/ocr2/part 512 MB iqn.2006-01.com.openfiler:racdb.voting1 /dev/iscsi/voting1/part 32 MB iqn.2006-01.com.openfiler:racdb.voting2 /dev/iscsi/voting2/part 32 MB iqn.2006-01.com.openfiler:racdb.voting3 /dev/iscsi/voting3/part 32 MB After creating the new iSCSI volumes from the SAN, they now need to be configured for access and bound to RAW devices by all Oracle RAC nodes in the database cluster.
- From all Oracle RAC nodes in the cluster as root, discover the five new iSCSI volumes from the SAN which will be used to store the voting disks and OCR files.
- Manually login to the new iSCSI targets from all Oracle RAC nodes in the cluster.
- Create a single primary partition on each of the five new iSCSI volumes that span the entire disk. Perform this from only one of the Oracle RAC nodes in the cluster:
- Re-scan the SCSI bus from all Oracle RAC nodes in the cluster:
- Create a shell script (/usr/local/bin/setup_raw_devices.sh) on all Oracle RAC nodes in the cluster to bind the five Oracle Clusterware component devices to RAW devices as follows:
From all Oracle RAC nodes in the cluster, change the permissions of the new shell script to execute:
Manually execute the new shell script from all Oracle RAC nodes in the cluster to bind the voting disks to RAW devices:
Check that the character (RAW) devices were created from all Oracle RAC nodes in the cluster:
Include the new shell script in /etc/rc.local to run on each boot from all Oracle RAC nodes in the cluster:
- Once the raw devices are created, use the dd command to zero out the device and make sure no data is written to the raw devices. Only perform this action from one of the Oracle RAC nodes in the cluster:
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Administering the OCR File
View OCR Configuration InformationAdd an OCR FileTwo methods exist to verify how many OCR files are configured for the cluster as well as their location. If the cluster is up and running, use the ocrcheck utility as either the oracle or root user account:
[oracle@racnode1 ~]$ ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4660 Available space (kbytes) : 257460 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile <-- OCR (primary) Device/File integrity check succeeded Device/File not configured <-- OCR Mirror (not configured) Cluster registry integrity check succeededIf CRS is down, you can still determine the location and number of OCR files by viewing the file ocr.loc, whose location is somewhat platform dependent. For example, on the Linux platform it is located in /etc/oracle/ocr.loc while on Sun Solaris it is located at /var/opt/oracle/ocr.loc:
[root@racnode1 ~]# cat /etc/oracle/ocr.loc ocrconfig_loc=/u02/oradata/racdb/OCRFile local_only=FALSETo view the actual contents of the OCR in a human-readable format, run the ocrdump command. This command requires the CRS stack to be running. Running the ocrdump command will dump the contents of the OCR into an ASCII text file in the current directory named OCRDUMPFILE:
The ocrdump utility also allows for different output options:
Starting with Oracle Clusterware 10g Release 2 (10.2), users now have the ability to multiplex (mirror) the OCR. Oracle Clusterware allows for a maximum of two OCR locations; one is the primary and the second is an OCR mirror. To avoid simultaneous loss of multiple OCR files, each copy of the OCR should be placed on a shared storage device that does not share any components (controller, interconnect, and so on) with the storage devices used for the other OCR file.
Before attempting to add a mirrored OCR, determine how many OCR files are currently configured for the cluster as well as their location. If the cluster is up and running, use the ocrcheck utility as either the oracle or root user account:
[oracle@racnode1 ~]$ ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4660 Available space (kbytes) : 257460 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile <-- OCR (primary) Device/File integrity check succeeded Device/File not configured <-- OCR Mirror (not configured yet) Cluster registry integrity check succeededIf CRS is down, you can still determine the location and number of OCR files by viewing the file ocr.loc, whose location is somewhat platform dependent. For example, on the Linux platform it is located in /etc/oracle/ocr.loc while on Sun Solaris it is located at /var/opt/oracle/ocr.loc:
[root@racnode1 ~]# cat /etc/oracle/ocr.loc ocrconfig_loc=/u02/oradata/racdb/OCRFile local_only=FALSEThe results above indicate I have only one OCR file and that it is located on an OCFS2 file system. Since we are allowed a maximum of two OCR locations, I intend to create an OCR mirror and locate it on the same OCFS2 file system in the same directory as the primary OCR. Please note that I am doing this for the sake brevity. The OCR mirror should always be placed on a separate device than the primary OCR file to guard against a single point of failure.
Note that the Oracle Clusterware stack should be online and running on all nodes in the cluster while adding, replacing, or removing the OCR location and hence does not require any system downtime.
The operations performed in this section affect the OCR for the entire cluster. However, the ocrconfig command cannot modify OCR configuration information for nodes that are shut down or for nodes on which Oracle Clusterware is not running. So, you should avoid shutting down nodes while modifying the OCR using the ocrconfig command. If for any reason, any of the nodes in the cluster are shut down while modifying the OCR using the ocrconfig command, you will need to perform a repair on the stopped node before it can brought online to join the cluster. Please see the section "Repair an OCR File on a Local Node" for instructions on repairing the OCR file on the affected node. You can add an OCR mirror after an upgrade or after completing the Oracle Clusterware installation. The Oracle Universal Installer (OUI) allows you to configure either one or two OCR locations during the installation of Oracle Clusterware. If you already mirror the OCR, then you do not need to add a new OCR location; Oracle Clusterware automatically manages two OCRs when you configure normal redundancy for the OCR. As previously mentioned, Oracle RAC environments do not support more than two OCR locations; a primary OCR and a secondary (mirrored) OCR.
Run the following command to add or relocate an OCR mirror using either destination_file or disk to designate the target location of the additional OCR:
ocrconfig -replace ocrmirrorocrconfig -replace ocrmirror
You must be logged in as the root user to run the ocrconfig command.
Please note that ocrconfig -replace is the only way to add/relocate OCR files/mirrors. Attempting to copy the existing OCR file to a new location and then manually adding/changing the file pointer in the ocr.loc file is not supported and will actually fail to work. For example:
After adding the new OCR mirror, check that it can be seen from all nodes in the cluster:
As mentioned earlier, you can have at most two OCR files in the cluster; the primary OCR and a single OCR mirror. Attempting to add an extra mirror will actually relocate the current OCR mirror to the new location specified in the command:
[root@racnode1 ~]# cp /dev/null /u02/oradata/racdb/OCRFile_mirror2 [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile_mirror2 [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile_mirror2 [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile_mirror2 [root@racnode1 ~]# ocrconfig -replace ocrmirror /u02/oradata/racdb/OCRFile_mirror2 [root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded Device/File Name : /u02/oradata/racdb/OCRFile_mirror2 <-- Mirror was Relocated! Device/File integrity check succeeded Cluster registry integrity check succeededRepair an OCR File on a Local NodeJust as we were able to add a new ocrmirror while the CRS stack was online, the same holds true when relocating an OCR file or OCR mirror and therefore does not require any system downtime.
You can relocate OCR only when the OCR is mirrored. A mirror copy of the OCR file is required to move the OCR online. If there is no mirror copy of the OCR, first create the mirror using the instructions in the previous section.
Attempting to relocate OCR when an OCR mirror does not exist will produce the following error:
ocrconfig -replace ocr /u02/oradata/racdb/OCRFile PROT-16: Internal ErrorIf the OCR mirror is not required in the cluster after relocating the OCR, it can be safely removed.
Run the following command as the root account to relocate the current OCR file to a new location using either destination_file or disk to designate the new target location for the OCR:
ocrconfig -replace ocrocrconfig -replace ocr Run the following command as the root account to relocate the current OCR mirror to a new location using either destination_file or disk to designate the new target location for the OCR mirror:
ocrconfig -replace ocrmirrorocrconfig -replace ocrmirror The following example assumes the OCR is mirrored and demonstrates how to relocate the current OCR file (/u02/oradata/racdb/OCRFile) from the OCFS2 file system to a new raw device (/dev/raw/raw1):
After relocating the OCR file, check that the change can be seen from all nodes in the cluster:
After verifying the relocation was successful, remove the old OCR file at the OS level:
It was mentioned in the previous section that the ocrconfig command cannot modify OCR configuration information for nodes that are shut down or for nodes on which Oracle Clusterware is not running. You may need to repair an OCR configuration on a particular node if your OCR configuration changes while that node is stopped. For example, you may need to repair the OCR on a node that was shut down while you were adding, replacing, or removing an OCR.
To repair an OCR configuration, run the following command as root from the node on which you have stopped the Oracle Clusterware daemon:
ocrconfig –repair ocr device_nameTo repair an OCR mirror configuration, run the following command as root from the node on which you have stopped the Oracle Clusterware daemon:
ocrconfig –repair ocrmirror device_name
You cannot perform this operation on a node on which the Oracle Clusterware daemon is running. The CRS stack must be shutdown before attempting to repair the OCR configuration on the local node. The ocrconfig –repair command changes the OCR configuration only on the node from which you run this command. For example, if the OCR mirror was relocated to a disk named /dev/raw/raw2 from racnode1 while the node racnode2 was down, then use the command ocrconfig -repair ocrmirror /dev/raw/raw2 on racnode2 while the CRS stack is down on that node to repair its OCR configuration:
To remove an OCR, you need to have at least one OCR online. You may need to perform this to reduce overhead or for other storage reasons, such as stopping a mirror to move it to SAN, RAID etc. Carry out the following steps:
- Check if at least one OCR is online
- Verify the CRS stack is online — preferably on all nodes
- Remove the OCR or OCR mirror
- If using a clustered file system, remove the deleted file at the OS level
Run the following command as the root account to delete the current OCR or the current OCR mirror:
ocrconfig -replace ocr or ocrconfig -replace ocrmirrorFor example:
After removing the new OCR mirror, check that the change is seen from all nodes in the cluster:
Removing the OCR or OCR mirror from the cluster configuration does not remove the physical file at the OS level when using a clustered file system.
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Backup the OCR File
There are two methods for backing up the contents of the OCR and each backup method can be used for different recovery purposes. This section discusses how to ensure the stability of the cluster by implementing a robust backup strategy.
The first type of backup relies on automatically generated OCR file copies which are sometimes referred to as physical backups. These physical OCR file copies are automatically generated by the CRSD process on the master node and are primarily used to recover the OCR from a lost or corrupt OCR file. Your backup strategy should include procedures to copy these automatically generated OCR file copies to a secure location which is accessible from all nodes in the cluster in the event the OCR needs to be restored.
The second type of backup uses manual procedures to create OCR export files; also known as logical backups. Creating a manual OCR export file should be performed both before and after making significant configuration changes to the cluster, such as adding or deleting nodes from your environment, modifying Oracle Clusterware resources, or creating a database. If in the event a configuration change is made to the OCR that causes errors, the OCR can be restored to a previous state by performing an import of the logical backup taken before the configuration change. Please note that an OCR logical export can also be used to restore the OCR from a lost or corrupt OCR file.
Unlike the methods used to backup the voting disk, attempting to backup the OCR by copying the OCR file directly at the OS level is not a valid backup and will result in errors after the restore! Because of the importance of OCR information, Oracle recommends that you make copies of the automatically created backup files and an OCR export at least once a day. The following is a working UNIX script that can be scheduled in CRON to backup the OCR File(s) and the Voting Disk(s) on a regular basis:
Automatic OCR Backupscrs_components_backup_10g.ksh
Manual OCR ExportsThe Oracle Clusterware automatically creates OCR physical backups every four hours. At any one time, Oracle always retains the last 3 backup copies of the OCR that are 4 hours old. The CRSD process that creates these backups also creates and retains an OCR backup for each full day and at the end of each week. You cannot customize the backup frequencies or the number of OCR physical backup files that Oracle retains.
The default location for generating physical backups on UNIX-based systems is CRS_home/cdata/cluster_name where cluster_name is the name of your cluster (i.e. crs). Use the ocrconfig -showbackup command to view all current OCR physical backups that were taken from the master node:
You can change the location where the CRSD process writes the physical OCR copies to using:
ocrconfig -backuplocRestoring the OCR from an automatic physical backup is accomplished using the ocrconfig -restore command. Note that the CRS stack needs to be shutdown on all nodes in the cluster prior to running the restore operation:
ocrconfig -restoreYou cannot restore the OCR from a physical backup using the -import option. The only method to restore the OCR from a physical backup is to use the -restore option.
The Master Node
As documented in Doc ID: 357262.1 on the My Oracle Support web site, the CRSD process only creates automatic OCR physical backups on one node in the cluster, which is the OCR master node. It does not create automatic backup copies on the other nodes; only from the OCR master node. If the master node fails, the OCR backups will be created from the new master node. You can determine which node in the cluster is the master node by examining the $ORA_CRS_HOME/log/
/cssd/ocssd.log file on any node in the cluster. In this log file, check for reconfiguration information (reconfiguration successful) after which you will see which node is the master and how many nodes are active in the cluster:
Another quick approach is to use either of the following methods:
# If not found in the ocssd.log, then look through all # of the ocssd archives: Node 1 - (racnode1) # for x in 'ls -tr $ORA_CRS_HOME/log/racnode?/cssd/ocssd.*' do grep -i "master node" $x; done | tail -1 [ CSSD]CLSS-3001: local node number 1, master node number 1 Node 2 - (racnode2) # for x in 'ls -tr $ORA_CRS_HOME/log/racnode?/cssd/ocssd.*' do grep -i "master node" $x; done | tail -1 [ CSSD]CLSS-3001: local node number 2, master node number 1
# The master node information is confirmed by the # ocrconfig -showbackup command: # ocrconfig -showbackup racnode1 2009/09/29 13:05:22 /u01/app/crs/cdata/crs racnode1 2009/09/29 09:05:22 /u01/app/crs/cdata/crs racnode1 2009/09/29 05:05:22 /u01/app/crs/cdata/crs racnode1 2009/09/28 05:05:21 /u01/app/crs/cdata/crs racnode1 2009/09/22 05:05:13 /u01/app/crs/cdata/crsBecause of the importance of OCR information, Oracle recommends that you make copies of the automatically created backup files at least once a day from the master node to a different device from where the primary OCR resides. You can use any backup software to copy the automatically generated physical backup files to a stable backup location:
It is possible and recommended that shared storage be used for the backup location(s). Keep in mind that if the master node goes down and cannot be rebooted, it is possible to loose all OCR physical backups if they were all on that node. The OCR backup process, however, will start on the new master node within four hours for all new backups. It is highly recommended that you integrate OCR backups with your normal database backup strategy. If possible, use a backup location that is shared by all nodes in the cluster.
Performing a manual export of the OCR should be done before and after making significant configuration changes to the cluster, such as adding or deleting nodes from your environment, modifying Oracle Clusterware resources, or creating a database. This type of backup is often referred to as a logical backup. If in the event a configuration change is made to the OCR that causes errors, the OCR can be restored to its previous state by performing an import of the logical backup taken before the configuration change. For example, if you have unresolvable configuration problems, or if you are unable to restart your cluster database after such changes, then you can restore your configuration by importing the saved OCR content from a valid configuration.
Please note that an OCR logical export can also be used to restore the OCR from a lost or corrupt OCR file.
To export the contents of the OCR to a dump file, use the following command, where backup_file_name is the name of the OCR logical backup file you want to create:
ocrconfig -exportFor example:
[root@racnode1 ~]# ocrconfig -export /u02/crs_backup/ocrbackup/RACNODE1/exports/OCRFileBackup.dmp # A second export is not strictly required, however, there is no such thing as too many backups! [root@racnode2 ~]# ocrconfig -export /u02/crs_backup/ocrbackup/RACNODE2/exports/OCRFileBackup.dmpTo restore the OCR from an export/logical backup, use the ocrconfig –import command. Note that the CRS stack needs to be shutdown on all nodes in the cluster prior to running the restore operation. In addition, the total space required for the restored OCR location (typically 280MB) has to be pre-allocated. This is especially important when the OCR is located on a clustered file system like OCFS2.
ocrconfig –importYou cannot restore the OCR from a logical backup using the -restore option. The only method to restore the OCR from a logical export is to use the -import option.
You must be logged in as the root user to run the ocrconfig command.
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Recover the OCR File
If an application fails, then before attempting to restore the OCR, restart the application. As a definitive verification that the OCR failed, run the ocrcheck command:
[root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded <-- OCR (primary) Valid Device/File Name : /u02/oradata/racdb/OCRFile_mirror Device/File integrity check succeeded <-- OCR (mirror) Valid Cluster registry integrity check succeededThe example above indicates that both the primary OCR and OCR mirror checks were successful and that no problems exist with the OCR configuration.
If the ocrcheck command does not display the message 'Device/File integrity check succeeded' for at least one copy of the OCR, then both the primary OCR and the OCR mirror have failed. In this case, the CRS stack must be brought down on all nodes in the cluster to restore the OCR from a previous physical backup copy or an OCR export.
If there is at least one copy of the OCR available (either the primary OCR or the OCR mirror), you can use that valid copy to restore the contents of the other copy of the OCR. The restore in this case can be accomplished using the ocrconfig -replace command and does not require the applications or CRS stack to be down.
This section describes a number of possible OCR recovery scenarios using the OCR configuration described by the output of the ocrcheck command above. Both the primary OCR and the OCR mirror are located on an OCFS2 file system in the same directory. The recovery scenarios demonstrated in this section will make use of both types of OCR backups — automatically generated OCR file copies and manually created OCR export files.
Recover OCR from Valid OCR Mirror
Although it should go without saying, DO NOT perform these recovery scenarios on a critical system like production! Recover OCR from Automatically Generated Physical BackupThis section demonstrates how to restore the OCR when only one of the OCR copies is missing or corrupt. The restore process will use the good OCR copy (whether its the primary OCR or the OCR mirror) to restore the missing/corrupt copy. Remember that if there is at least one copy of the OCR available, you can use that valid copy to restore the contents of the other copy of the OCR. The best part about this type of recovery is that it doesn't require any downtime! Oracle Clusterware and the applications can remain online during the recovery process.
For the purpose of this example, let's corrupt the primary OCR file:
Running ocrcheck picks up the now corrupted primary OCR file:
[root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile <-- Corrupt OCR Device/File needs to be synchronized with the other device Device/File Name : /u02/oradata/racdb/OCRFile_mirror Device/File integrity check succeeded Cluster registry integrity check succeededNote that after loosing the one OCR copy (in this case, the primary OCR file), Oracle Clusterware and the applications remain online:
While the applications and CRS remain online, perform the following steps to recover the primary OCR using the contents of the OCR mirror.
- When using a clustered file system, remove the corrupt OCR file and re-initialize it:
[root@racnode1 ~]# rm /u02/oradata/racdb/OCRFile [root@racnode1 ~]# cp /dev/null /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile
NOTE: If the target OCR is located on a raw device, verify the permissions are applied correctly for an OCR file (owned by root:oinstall with 0640 permissions), that the device is being shared by all nodes in the cluster, and finally use the dd command from only one node in the cluster to zero out the device and make sure no data is written to the raw device.
[root@racnode1 ~]# ls -l /dev/raw/raw1 crw-r----- 1 root oinstall 162, 1 Oct 6 11:05 /dev/raw/raw1 [root@racnode2 ~]# ls -l /dev/raw/raw1 crw-r----- 1 root oinstall 162, 1 Oct 6 11:04 /dev/raw/raw1 [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw1- Restore the primary OCR using the contents of the OCR mirror. Note that this operation is the same process used when adding a new OCR location:
[root@racnode1 ~]# ocrconfig -replace ocr /u02/oradata/racdb/OCRFile
NOTE: If the target OCR is located on a raw device, substitute the path name above with that of the shared device name: (i.e. /dev/raw/raw1)
- Verify the restore was successful by viewing the Clusterware alert log file.
[root@racnode1 ~]# tail $ORA_CRS_HOME/log/racnode1/alertracnode1.log ... 2009-10-06 17:46:51.118 [crsd(11054)]CRS-1007:The OCR/OCR mirror location was replaced by /u02/oradata/racdb/OCRFile.- Verify the OCR configuration by running the ocrcheck command:
[root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded <-- Primary OCR Restored Device/File Name : /u02/oradata/racdb/OCRFile_mirror Device/File integrity check succeeded Cluster registry integrity check succeeded- As the oracle user account with user equivalence enabled on all the nodes, run the cluvfy command to validate the OCR configuration:
[oracle@racnode1 ~]$ ssh racnode1 "hostname; date" racnode1 Tue Oct 6 17:52:52 EDT 2009 [oracle@racnode1 ~]$ ssh racnode2 "hostname; date" racnode2 Tue Oct 6 17:51:50 EDT 2009 [oracle@racnode1 ~]$ cluvfy comp ocr -n all Verifying OCR integrity Checking OCR integrity... Checking the absence of a non-clustered configuration... All nodes free of non-clustered, local-only configurations. Uniqueness check for OCR device passed. Checking the version of OCR... OCR of correct Version "2" exists. Checking data integrity of OCR... Data integrity check for OCR passed. OCR integrity check passed. Verification of OCR integrity was successful.Recover OCR from an OCR Export FileThis section demonstrates how to recover the Oracle Cluster Registry from a lost or corrupt OCR file. This example assumes that both the primary OCR and the OCR mirror are lost from an accidental delete by a user and that the latest automatic OCR backup copy on the master node is accessible.
At this time, the second node in the cluster (racnode2) is the master node and currently available. We will be restoring the OCR using the latest OCR backup copy from racnode2 which is located at /u01/app/crs/cdata/crs/backup00.ocr.
Let's now corrupt the OCR by removing both the primary OCR and the OCR mirror:
Running ocrcheck fails to provide any useful information given that both OCR files are lost
[root@racnode1 ~]# ocrcheck PROT-602: Failed to retrieve data from the cluster registryNote that after loosing both OCR files, Oracle Clusterware and the applications remain online. Before restoring the OCR, the applications and CRS will need to be shutdown as described in the steps below.
Perform the following steps to recover the OCR from the latest automatically generated physical backup:
- With CRS still online, identify the master node (which in this example is racnode2) and all OCR backups using the ocrconfig -showbackup command:
[root@racnode1 ~]# ocrconfig -showbackup racnode2 2009/10/07 12:05:18 /u01/app/crs/cdata/crs racnode2 2009/10/07 08:05:17 /u01/app/crs/cdata/crs racnode2 2009/10/07 04:05:17 /u01/app/crs/cdata/crs racnode2 2009/10/07 00:05:16 /u01/app/crs/cdata/crs racnode1 2009/09/24 08:49:19 /u01/app/crs/cdata/crsNote that ocrconfig -showbackup may result in a segmentation fault or simply not show any results if CRS is shutdown.
- For documentation purposes, identify the number and location of all configured OCR files that will be recovered in this example.
[root@racnode2 ~]# cat /etc/oracle/ocr.loc #Device/file /u02/oradata/racdb/OCRFile getting replaced by device /u02/oradata/racdb/OCRFile ocrconfig_loc=/u02/oradata/racdb/OCRFile ocrmirrorconfig_loc=/u02/oradata/racdb/OCRFile_mirror- Although all OCR files have been lost or corrupted, the Oracle Clusterware daemons as well as the clustered database remain running. In this scenario, Oracle Clusterware and all managed resources need to be shut down in order to recover the OCR. Attempting to stop CRS using crsctl stop crs will fail given it cannot write to the now lost/corrupt OCR file:
[root@racnode1 ~]# crsctl stop crs OCR initialization failed accessing OCR device: PROC-26: Error while accessing the physical storage Operating System error [No such file or directory] [2]With the environment in this unstable state, shutdown all database instances from all nodes in the cluster and then reboot each node:
[oracle@racnode1 ~]$ sqlplus / as sysdba SQL> shutdown immediate [root@racnode1 ~]# reboot ------------------------------------------------ [oracle@racnode2 ~]$ sqlplus / as sysdba SQL> shutdown immediate [root@racnode2 ~]# reboot- When the Oracle RAC nodes come back up, note that Oracle Clusterware will fail to start as a result of the lost/corrupt OCR file:
[root@racnode1 ~]# crs_stat -t CRS-0184: Cannot communicate with the CRS daemon. [root@racnode2 ~]# crs_stat -t CRS-0184: Cannot communicate with the CRS daemon.- When using a clustered file system, re-initialize both the primary OCR and the OCR mirror target locations identified earlier in the /etc/oracle/ocr.loc file:
[root@racnode1 ~]# rm -f /u02/oradata/racdb/OCRFile [root@racnode1 ~]# cp /dev/null /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile [root@racnode1 ~]# rm -f /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# cp /dev/null /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile_mirror
NOTE: If the target OCR is located on a raw device(s), verify the permissions are applied correctly for an OCR file (owned by root:oinstall with 0640 permissions), that the device is being shared by all nodes in the cluster, and finally use the dd command from only one node in the cluster to zero out the device(s) and make sure no data is written to the raw device(s).
[root@racnode1 ~]# ls -l /dev/raw/raw[12] crw-r----- 1 root oinstall 162, 1 Oct 7 15:00 /dev/raw/raw1 crw-r----- 1 root oinstall 162, 2 Oct 7 15:00 /dev/raw/raw2 [root@racnode2 ~]# ls -l /dev/raw/raw[12] crw-r----- 1 root oinstall 162, 1 Oct 7 14:59 /dev/raw/raw1 crw-r----- 1 root oinstall 162, 2 Oct 7 14:59 /dev/raw/raw2 [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw1 <-- OCR (primary) [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw2 <-- OCR (mirror)- Before restoring the OCR, dump the contents of the physical backup you intend to recover from the master node (racnode2) to validate its availability as well as the accuracy of its contents:
[root@racnode2 ~]# ocrdump -backupfile /u01/app/crs/cdata/crs/backup00.ocr [root@racnode2 ~]# less OCRDUMPFILE- With CRS down, perform the restore operation from the master node (racnode2) by applying the latest automatically generated physical backup:
[root@racnode2 ~]# ocrconfig -restore /u01/app/crs/cdata/crs/backup00.ocr- Restart Oracle Clusterware on all of the nodes in the cluster by rebooting each node or by running the crsctl start crs command:
[root@racnode1 ~]# crsctl start crs Attempting to start CRS stack The CRS stack will be started shortly [root@racnode2 ~]# crsctl start crs Attempting to start CRS stack The CRS stack will be started shortly- Verify the OCR configuration by running the ocrcheck command:
[root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded <-- Primary OCR Restored Device/File Name : /u02/oradata/racdb/OCRFile_mirror Device/File integrity check succeeded <-- Mirror OCR Restored Cluster registry integrity check succeeded- As the oracle user account with user equivalence enabled on all the nodes, run the cluvfy command to validate the OCR configuration:
[oracle@racnode1 ~]$ ssh racnode1 "hostname; date" racnode1 Wed Oct 7 16:29:49 EDT 2009 [oracle@racnode1 ~]$ ssh racnode2 "hostname; date" racnode2 Wed Oct 7 16:29:06 EDT 2009 [oracle@racnode1 ~]$ cluvfy comp ocr -n all Verifying OCR integrity Checking OCR integrity... Checking the absence of a non-clustered configuration... All nodes free of non-clustered, local-only configurations. Uniqueness check for OCR device passed. Checking the version of OCR... OCR of correct Version "2" exists. Checking data integrity of OCR... Data integrity check for OCR passed. OCR integrity check passed. Verification of OCR integrity was successful.- Finally, verify the applications are running:
[root@racnode1 ~]# crs_stat -t Name Type Target State Host ------------------------------------------------------------ ora.racdb.db application ONLINE ONLINE racnode1 ora....b1.inst application ONLINE ONLINE racnode1 ora....b2.inst application ONLINE ONLINE racnode2 ora....srvc.cs application ONLINE ONLINE racnode2 ora....db1.srv application ONLINE ONLINE racnode1 ora....db2.srv application ONLINE ONLINE racnode2 ora....SM1.asm application ONLINE ONLINE racnode1 ora....E1.lsnr application ONLINE ONLINE racnode1 ora....de1.gsd application ONLINE ONLINE racnode1 ora....de1.ons application ONLINE ONLINE racnode1 ora....de1.vip application ONLINE ONLINE racnode1 ora....SM2.asm application ONLINE ONLINE racnode2 ora....E2.lsnr application ONLINE ONLINE racnode2 ora....de2.gsd application ONLINE ONLINE racnode2 ora....de2.ons application ONLINE ONLINE racnode2 ora....de2.vip application ONLINE ONLINE racnode2This section demonstrates how to restore the Oracle Cluster Registry to a valid state after an OCR configuration change causes unresolvable errors and renders the cluster as unusable. This example can also be used to recover the OCR from a lost / corrupt OCR file. It is assumed a manual OCR export was taken prior to making the OCR configuration change that caused problems with the cluster registry:
Perform the following steps to restore the previous configuration stored in the OCR from an OCR export file:
- For documentation purposes, identify the number and location of all configured OCR files that will be recovered in this example.
[root@racnode2 ~]# cat /etc/oracle/ocr.loc #Device/file /u02/oradata/racdb/OCRFile getting replaced by device /u02/oradata/racdb/OCRFile ocrconfig_loc=/u02/oradata/racdb/OCRFile ocrmirrorconfig_loc=/u02/oradata/racdb/OCRFile_mirror- Place the OCR export file that you created previously using the ocrconfig -export command on a local disk for the node that will be performing the import:
[root@racnode1 ~]# mkdir -p /u03/crs_backup/ocrbackup/exports [root@racnode1 ~]# cd /u02/crs_backup/ocrbackup/RACNODE1/exports [root@racnode1 ~]# cp -p OCRFileBackup.dmp /u03/crs_backup/ocrbackup/exports [root@racnode1 ~]# ls -l /u03/crs_backup/ocrbackup/exports total 112 -rw-r--r-- 1 root root 110233 Oct 8 09:38 OCRFileBackup.dmp
NOTE: The ocrconfig -import process is unable to read an OCR export file from an OCFS2 file system. Attempting to import an OCR export file that is located on an OCFS2 file system will fail with the following error:
[root@racnode1 ~]# ocrconfig -import /u02/crs_backup/ocrbackup/RACNODE1/exports/OCRFileBackup.dmp PROT-8: Failed to import data from specified file to the cluster registryInvestigating the $ORA_CRS_HOME/log//client/ocrconfig_pid.log will reveal the error:... [ OCRCONF][3012240]Error[112] encountered when reading from import file ...The solution is to copy the OCR dump file to be imported from the OCFS2 file system to a file system on the local disk.- As the root user, stop Oracle Clusterware on all the nodes in the cluster by executing the following command:
[root@racnode1 ~]# crsctl stop crs Stopping resources. This could take several minutes. Error while stopping resources. Possible cause: CRSD is down. [root@racnode2 ~]# crsctl stop crs Stopping resources. This could take several minutes. Error while stopping resources. Possible cause: CRSD is down.- When using a clustered file system, re-initialize / pre-allocate the space (typically 280MB) for both the primary OCR and the OCR mirror target locations identified earlier in the /etc/oracle/ocr.loc file:
[root@racnode1 ~]# rm -f /u02/oradata/racdb/OCRFile [root@racnode1 ~]# dd if=/dev/zero of=/u02/oradata/racdb/OCRFile bs=4096 count=65587 [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile [root@racnode1 ~]# rm -f /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# dd if=/dev/zero of=/u02/oradata/racdb/OCRFile_mirror bs=4096 count=65587 [root@racnode1 ~]# chown root /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# chgrp oinstall /u02/oradata/racdb/OCRFile_mirror [root@racnode1 ~]# chmod 640 /u02/oradata/racdb/OCRFile_mirror
NOTE: If the target OCR is located on a raw device(s), verify the permissions are applied correctly for an OCR file (owned by root:oinstall with 0640 permissions), that the device is being shared by all nodes in the cluster, and finally use the dd command from only one node in the cluster to zero out the device(s) and make sure no data is written to the raw device(s).
[root@racnode1 ~]# ls -l /dev/raw/raw[12] crw-r----- 1 root oinstall 162, 1 Oct 8 09:43 /dev/raw/raw1 crw-r----- 1 root oinstall 162, 2 Oct 8 09:43 /dev/raw/raw2 [root@racnode2 ~]# ls -l /dev/raw/raw[12] crw-r----- 1 root oinstall 162, 1 Oct 8 09:42 /dev/raw/raw1 crw-r----- 1 root oinstall 162, 2 Oct 8 09:42 /dev/raw/raw2 [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw1 <-- OCR (primary) [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw2 <-- OCR (mirror)- With CRS down as the root user, restore the OCR data by importing the contents of the OCR export file using the following command:
[root@racnode1 ~]# ocrconfig -import /u03/crs_backup/ocrbackup/exports/OCRFileBackup.dmp- Restart Oracle Clusterware on all of the nodes in the cluster by rebooting each node or by running the crsctl start crs command:
[root@racnode1 ~]# crsctl start crs Attempting to start CRS stack The CRS stack will be started shortly [root@racnode2 ~]# crsctl start crs Attempting to start CRS stack The CRS stack will be started shortly- Verify the OCR configuration by running the ocrcheck command:
[root@racnode1 ~]# ocrcheck Status of Oracle Cluster Registry is as follows : Version : 2 Total space (kbytes) : 262120 Used space (kbytes) : 4668 Available space (kbytes) : 257452 ID : 1331197 Device/File Name : /u02/oradata/racdb/OCRFile Device/File integrity check succeeded <-- Primary OCR Restored Device/File Name : /u02/oradata/racdb/OCRFile_mirror Device/File integrity check succeeded <-- Mirror OCR Restored Cluster registry integrity check succeeded- As the oracle user account with user equivalence enabled on all the nodes, run the cluvfy command to validate the OCR configuration:
[oracle@racnode1 ~]$ ssh racnode1 "hostname; date" racnode1 Thu Oct 8 11:34:15 EDT 2009 [oracle@racnode1 ~]$ ssh racnode2 "hostname; date" racnode2 Thu Oct 8 11:33:33 EDT 2009 [oracle@racnode1 ~]$ cluvfy comp ocr -n all Verifying OCR integrity Checking OCR integrity... Checking the absence of a non-clustered configuration... All nodes free of non-clustered, local-only configurations. Uniqueness check for OCR device passed. Checking the version of OCR... OCR of correct Version "2" exists. Checking data integrity of OCR... Data integrity check for OCR passed. OCR integrity check passed. Verification of OCR integrity was successful.- Finally, verify the applications are running:
[root@racnode1 ~]# crs_stat -t Name Type Target State Host ------------------------------------------------------------ ora.racdb.db application ONLINE ONLINE racnode1 ora....b1.inst application ONLINE ONLINE racnode1 ora....b2.inst application ONLINE ONLINE racnode2 ora....srvc.cs application ONLINE ONLINE racnode2 ora....db1.srv application ONLINE ONLINE racnode1 ora....db2.srv application ONLINE ONLINE racnode2 ora....SM1.asm application ONLINE ONLINE racnode1 ora....E1.lsnr application ONLINE ONLINE racnode1 ora....de1.gsd application ONLINE ONLINE racnode1 ora....de1.ons application ONLINE ONLINE racnode1 ora....de1.vip application ONLINE ONLINE racnode1 ora....SM2.asm application ONLINE ONLINE racnode2 ora....E2.lsnr application ONLINE ONLINE racnode2 ora....de2.gsd application ONLINE ONLINE racnode2 ora....de2.ons application ONLINE ONLINE racnode2 ora....de2.vip application ONLINE ONLINE racnode2
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Administering the Voting Disk
View Voting Disk Configuration InformationAdd a Voting DiskUse the crsctl utility to verify how many voting disks are configured for the cluster as well as their location. The the crsctl command can be run as either the oracle or root user account:
[oracle@racnode1 ~]$ crsctl query css votedisk 0. 0 /u02/oradata/racdb/CSSFile located 1 votedisk(s).Remove a Voting DiskAdding or removing a voting disk from the cluster is a fairly straightforward process. Oracle Clusterware 10g Release 1 (10.1) only allowed for one voting disk while Oracle Oracle Clusterware 10g Release 2 (10.2) lifted this restriction to allow for 32 voting disks. Having multiple voting disks available to the cluster removes the voting disk as a single point of failure and eliminates the need to mirror them outside of Oracle Clusterware (i.e. RAID). The Oracle Universal Installer (OUI) allows you to configure either one or three voting disks during the installation of Oracle Clusterware. Having three voting disks available allows Oracle Clusterware (CRS) to continue operating uninterrupted when any one of the voting disks fail.
When deciding how many voting disks is appropriate for your environment, consider that for the cluster to survive failure of x number of voting disks, you need to configure (2x + 1) voting disks. For example, to allow for the failure of 2 voting disks, you would need to configure 5 voting disks. When allocating shared raw storage devices for the voting disk(s), keep in mind that each voting disk requires 20MB of raw storage.
OCR Corruption after Adding/Removing Voting Disk when CRS Stack is RunningIn addition to allowing for more than one voting disk in the cluster, the Oracle10g R2 documentation also indicates that adding and removing voting disks can be performed while CRS is online and does not require any cluster-wide downtime. After reading of this new capability, I immediately tried adding a new voting while CRS was running only to be greeted with the following error:
[root@racnode1 ~]# crsctl add css votedisk /dev/raw/raw3 Cluster is not in a ready state for online disk additionAfter some research, it appears this is a known issue on at least the Linux and Sun Solaris platform with the 10.2.0.1.0 release and is fully documented in Oracle Bug 4898020: ADDING VOTING DISK ONLINE CRASH THE CRS. Some have reported that this issue was to be fixed with the 10.2.0.4 patch set; however that is the release I am currently using and the bug still exists.
In order to workaround this bug, you must first shut down CRS and then use the -force flag when running the crsctl command. Do not attempt to add or remove a voting disk to the cluster using the -force flag while CRS is online. Oracle Clusterware should be shut down on all nodes in the cluster before adding or removing voting disks.
Using the -force flag to add or remove a voting disk while the Oracle Clusterware stack is active on any node in the cluster may corrupt your cluster configuration.
Bring down CRS on all nodes in the cluster prior to modifying the voting disk configuration using the -force flag to avoid interacting with active Oracle Clusterware daemons.
If the Oracle Clusterware stack is online while attempting to use the -force flag, all nodes in the cluster will reboot due to the css shutdown and corruption of your cluster configuration is very likely.
For a detailed discussion on this issue, please see Oracle Doc ID: 390880.1 "OCR Corruption after Adding/Removing voting disk to a cluster when CRS stack is running) on the My Oracle Support web site.
To add a new voting disk to the cluster, use the following command where path is the fully qualified path for the additional voting disk. Run the following command as the root user to add a voting disk:
crsctl add css votedisk
You must be logged in as the root user to run the crsctl command to add/remove voting disks. The following example demonstrates how to add two new voting disks to the current cluster. The new voting disks will reside on the same OCFS2 file system in the same directory as the current voting disk. Please note that I am doing this for the sake brevity. Multiplexed voting disks should always be placed on a separate device than the current voting disk to guard against a single point of failure.
Stop all application processes, shut down CRS on all nodes, and Oracle10g R2 users should use the -force flag to the crsctl command when adding the new voting disk(s). For example:
If the new voting disks will be created on raw devices # # Clear out the contents from the new raw devices. # [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw3 [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw4 # # Add two new voting disks. # [root@racnode1 ~]# crsctl add css votedisk /dev/raw/raw3 -force Now formatting voting disk: /dev/raw/raw3 successful addition of votedisk /dev/raw/raw3. [root@racnode1 ~]# crsctl add css votedisk /dev/raw/raw4 -force Now formatting voting disk: /dev/raw/raw4 successful addition of votedisk /dev/raw/raw4.After adding the new voting disk(s), check that they can be seen from all nodes in the cluster:
After verifying the new voting disk(s) can be seen from all nodes in the cluster, restart CRS and the application processes:
As discussed in the previous section, Oracle Clusterware must be shut down on all nodes in the cluster before adding or removing voting disks. Just as we were required to add the -force flag when adding a voting disk, the same holds true for Oracle10g R2 users attempting to remove a voting disk:
The CRS stack must be shutdown on all nodes in the the cluster before attempting to use the -force flag. Failure to do so may result in OCR corruption.
Use the following command as the root user to remove a voting disk where path is the fully qualified path for the voting disk to be removed:
crsctl delete css votedisk
You must be logged in as the root user to run the crsctl command to add/remove voting disks. The "crsctl delete css votedisk" command deletes an existing voting disk from the cluster. This command does not, however, remove the physical file at the OS level if using a clustered file system nor does it clear the data from a raw storage device.
The following example demonstrates how to delete two voting disks from the current cluster. Stop all application processes, shut down CRS on all nodes, and Oracle10g R2 users should use the -force flag to the crsctl command when removing a voting disk(s). For example:
If the voting disks are on raw devices # # Remove two voting disks. # [root@racnode1 ~]# crsctl delete css votedisk /dev/raw/raw3 -force successful deletion of votedisk /dev/raw/raw3. [root@racnode1 ~]# crsctl delete css votedisk /dev/raw/raw4 -force successful deletion of votedisk /dev/raw/raw4. # # (Optional) # Clear out the old contents (voting disk data) from the raw devices. # [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw3 [root@racnode1 ~]# dd if=/dev/zero of=/dev/raw/raw4After removing the voting disk(s), check that the voting disk(s) were removed from the cluster and the new voting disk configuration is seen from all nodes in the cluster:
After verifying the voting disk(s) have been removed, restart CRS and the application processes on all nodes in the cluster:
The process of moving a voting disk consists simply of removing the old voting disk and adding a new voting disk to the destination location:
crsctl delete css votedisk-force crsctl add css votedisk -force As discussed earlier in this section, Oracle Clusterware must be shut down on all nodes in the cluster before adding or removing voting disks. Oracle10g R2 users are required to add the -force flag when removing/adding a voting disk. The CRS stack must be shutdown on all nodes in the the cluster before attempting to use the -force flag. Failure to do so may result in OCR corruption.
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Backup the Voting Disk
Backing up the voting disk(s) is often performed on a regular basis by the DBA to guard the cluster against a single point of failure as the result of hardware failure or user error. Because the node membership information does not usually change, it is not a strict requirement that you back up the voting disk every day. At a minimum, however, your backup strategy should include procedures to back up all voting disks at the following times and make certain that the backups are stored in a secure location that is accessible from all nodes in the cluster in the event the voting disk(s) need to be restored:
- After installing Oracle Clusterware
- After adding nodes to or deleting nodes from the cluster
- After performing voting disk add or delete operations
Oracle Clusterware 10g Release 1 (10.1) only allowed for one voting disk while Oracle Clusterware 10g Release 2 (10.2) lifted this restriction to allow for 32 voting disks. For high availability, Oracle recommends that Oracle Clusterware 10g R2 users configure multiple voting disks while keeping in mind that you must have an odd number of voting disks, such as three, five, and so on. To avoid simultaneous loss of multiple voting disks, each voting disk should be placed on a shared storage device that does not share any components (controller, interconnect, and so on) with the storage devices used for the other voting disks. If you define a single voting disk, then you should use external mirroring to provide redundancy.
To make a backup copy of the voting disk on UNIX/Linux, use the dd command:
dd if=of= bs= Perform this operation on every voting disk where voting_disk_name is the name of the active voting disk (input file), backup_file_name is the name of the file to which you want to back up the voting disk contents (output file), and block_size is the value to set both the input and output block sizes. As a general rule on most platforms, including Linux and Sun, the block size for the dd command should be 4k to ensure that the backup of the voting disk gets complete blocks.
If your voting disk is stored on a raw device, use the device name in place of voting_disk_name. For example:
dd if=/dev/raw/raw3 of=/u03/crs_backup/votebackup/VotingDiskBackup.dmp bs=4kWhen you use the dd command to make backups of the voting disk, the backup can be performed while the Cluster Ready Services (CRS) process is active; you do not need to stop the CRS daemons (namely, the crsd.bin process) before taking a backup of the voting disk.
The following is a working UNIX script that can be scheduled in CRON to backup the OCR File and the Voting Disk on a regular basis:
For the purpose of this example, the current Oracle Clusterware environment is configured with three voting disks on an OCFS2 clustered file system that will be backed up to a local file system on one of the nodes in the cluster. For example:
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Recover the Voting Disk
The recommended way to recover from a lost or corrupt voting disk is to restore it from a previous good backup that was taken with the dd command.
There are actually very few steps required to restore the voting disks:
- Shutdown CRS on all nodes in the cluster.
- List the current location of the voting disks.
- Restore each of the voting disks using the dd command from a previous good backup of the voting disks that was taken using the same dd command.
- Re-start CRS on all nodes in the cluster.
For example:
of= bs=4k [root@racnode1 ~]# crsctl start crs [root@racnode2 ~]# crsctl start crs The following is an example of what occurs on all RAC nodes when a voting disk is destroyed. This example will manually corrupt all voting disks in the cluster. After the Oracle RAC nodes reboot from the crash, we will follow up with the steps required to restore the lost/corrupt voting disk which will make use of the voting disk backups that were created in the previous section.
Although it should go without saying, DO NOT perform this recovery scenario on a critical system like production! First, let's check the status of the cluster and all RAC components, list the current location of the voting disk(s), and finally list the voting disk backup that will be used to recover from:
The next step is to simulate the corruption or loss of the voting disk(s).
Oracle RAC 10g R1 / R2 (not patched with 10.2.0.4)Oracle RAC 11g or higher (including Oracle RAC 10g R2 patched with 10.2.0.4)If you are using Oracle RAC 10g R1 or Oracle RAC 10g R2 (not patched with 10.2.0.4), simply write zero's to one of the voting disk:
[root@racnode1 ~]# dd if=/dev/zero of=/u02/oradata/racdb/CSSFile Both RAC servers are now stuck and will be rebooted by CRS...Starting with Oracle RAC 11g R1 (including Oracle RAC 10g R2 patched with 10.2.0.4), attempting to corrupt a voting disk using dd will result in all nodes being rebooted, however, Oracle Clusterware will re-construct the corrupt voting disk and successfully bring up the RAC components. Because the voting disks do not contain persistent data, CSSD is able to fully reconstruct the voting disks so long as the cluster is running. This feature was introduced with Oracle Clusterware 11.1 and is also available with Oracle Clusterware 10.2 patched with 10.2.0.4.
This makes it a bit more difficult to corrupt a voting disk by simply writing zero's to it. You would need to find a way to dd the voting disks and stop the cluster before any of the voting disks could be automatically recovered by CSSD. Good luck with that! To simulate the corruption (actually the loss) of the voting disk and have both nodes crash, I'm simply going to delete all of the voting disks and then manually reboot the nodes:
After the reboot, CRS will not come up and all RAC components will be down:
Ok, let's start the recovery process.
If you have multiple voting disks, then you can remove the voting disks and add them back into your environment using the crsctl delete css votedisk path and crsctl add css votedisk path commands respectively, where path is the complete path of the location on which the voting disk resides. After recovering the voting disk, run through several tests to verify that Oracle Clusterware is functioning correctly:
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Move the Voting Disk and OCR from OCFS to RAW Devices
This section provides instructions on how to move the OCR and all voting disks used throughout this article from an OCFS2 file system to raw storage devices.
Move the OCR
OCR / Voting Disk Mappings from OCFS2 to Raw Storage OCR Component Current Location on OCFS2 New Location OCR File (primary) /u02/oradata/racdb/OCRFile /dev/raw/raw1 OCR File (mirror) /u02/oradata/racdb/OCRFile_mirror /dev/raw/raw2 Vote Disk 1 /u02/oradata/racdb/CSSFile /dev/raw/raw3 Vote Disk 2 /u02/oradata/racdb/CSSFile_mirror1 /dev/raw/raw4 Vote Disk 3 /u02/oradata/racdb/CSSFile_mirror2 /dev/raw/raw5 Move the Voting Disk
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About the Author
Jeffrey Hunter is an Oracle Certified Professional, Java Development Certified Professional, Author, and an Oracle ACE. Jeff currently works as a Senior Database Administrator for The DBA Zone, Inc. located in Pittsburgh, Pennsylvania. His work includes advanced performance tuning, Java and PL/SQL programming, developing high availability solutions, capacity planning, database security, and physical / logical database design in a UNIX / Linux server environment. Jeff's other interests include mathematical encryption theory, tutoring advanced mathematics, programming language processors (compilers and interpreters) in Java and C, LDAP, writing web-based database administration tools, and of course Linux. He has been a Sr. Database Administrator and Software Engineer for over 20 years and maintains his own website site at: http://www.iDevelopment.info. Jeff graduated from Stanislaus State University in Turlock, California, with a Bachelor's degree in Computer Science and Mathematics.