11gR2 – having a second OCR file on a separate diskgroup

 

Oracle database versions  < 11gR2 RAC, the OUI had a screen where we could specify multiple OCR and or Voting disks.  Starting with 11gR2 since the OCR and Voting disks are stored on ASM storage we don’t have options to specify multiple OCR or for that matter multiple voting disks. Well do we need multiple disks for OCR and voting disks.  with these files stored on ASM, we could take advantage of the ASM mirroring options.  Normal Redundancy (two copies of the file), High Redundancy (three copies of the file) or External Redundancy (where ASM does not manage the redundant copy of these files, but the redundancy is maintained /protected at the storage level by mirroring disks.

If the normal redundancy option or the high redundancy option was selected when the disk group that stores the OCR/voting disks, the automatically the disks are mirrored for either normal or high redundancy.

Now what if we do not want to use ASM mirroring.. but would like the clusterware to maintain two or more copies of OCR files on physically different diskgroups.  Oracle supports this option, not while installing the Grid infrastructure but after the installation is  complete using the ocrconfig utility. Lets go through one such scenario.

OCR is a critical component of the RAC architecture.  From the point that the clusterware starts (on server start/reboot)and to start all applications running on the clusterware which includes database, listener, ASM, database services etc, the OCR is consulted by the clusterware for placement of resources.   OCR contains all the rules for high availability of these resources. The clusterware will use these definitions for placement of resources when an server / instance crashes.  In 11gR2 the OCR contains additional information such as server pool definitions etc.

The first time the clusterware starts it determines the location of the OCR file by checking the following location

1.  Request storage administrators to create a new LUN with the same size as the LUN that currently hosts the OCR and voting disks for the 11gR2 cluster

2.  Connect to the ASM instance on one for the database servers and create a new disk group and mount the disk group on all instances in the cluster using the following syntax

CREATE DISKGROUP PRD_GRID2 EXTERNAL REDUNDANCY ADD DISK ‘ ‘;

ALTER DISKGROUP PRD_GRID2 MOUNT

3. Once the diskgroup have been mounted..we can configure the diskgroup for OCR.   This configuration requires root privileges. 

Connect to the server as root. and execute ocrconfig command from the GRID_HOME /bin directory. 

[root@prddb3 bin]# ./ocrconfig -add +PRD_GRID2

Note:  if the disk group does not have the required privileges then you can get the following error.   I ran into this error while configuring OCR on PRD_GRID2 diskgroup.

PROT-30: The Oracle Cluster Registry location to be added is not accessible.

Also reported in the GRID_HOME/log/prddb3/client directory is a ocrconfig log file that contains the following errors

[root@prddb3 bin]# cat /app/grid/product/11.2.0/log/prddb3/client/ocrconfig_4000.log
Oracle Database 11g Clusterware Release 11.2.0.1.0 - Production Copyright 1996, 2009 Oracle. All rights reserved.
2010-07-10 20:38:18.472: [ OCRCONF][2833243664]ocrconfig starts...
2010-07-10 20:38:23.140: [  OCRCLI][2833243664]proac_replace_dev:[+PRD_GRID2]: Failed. Retval [8]
2010-07-10 20:38:23.140: [  OCRAPI][2833243664]procr_replace_dev: failed to replace device (8)
2010-07-10 20:38:23.140: [ OCRCONF][2833243664]The new OCR device [+PRD_GRID2] cannot be opened
2010-07-10 20:38:23.140: [ OCRCONF][2833243664]Exiting [status=failed]... 

What does this error mean?  by default when you create a diskgroup in 11gR2 RAC from the command prompt using SQL plus, the default compatibility attribute of the diskgroup is set to 10.1. This issue does not occur if you create it through ASMCA.

[oracle@prddb3]# sqlplus ‘ /as sysasm’

SQL> SELECT NAME,COMPATIBILITY,DATABASE_COMPATIBILITY from v$asm_diskgroup; 

NAME         COMPATIBILITY        DATABASE_COMPATIBILI VOT
------------ -------------------- -------------------- ---
PRD_DATA    11.2.0.0.0           11.2.0.0.0           N
PRD_FRA     11.2.0.0.0           11.2.0.0.0           N
PRD_GRID1   11.2.0.0.0           11.2.0.0.0           N
PRD_GRID2   10.1.0.0.0           10.1.0.0.0           N

Note The ASM compatibility and the database (RDBMS) compatibility defaults to 10.1. This needs to be changed to 11.2  in order for the clusterware to recognize that this is a 11gR2 ASM configuration.

4. Change the compatibility of the new diskgroup to 11.2 as follows:

ALTER DISKGROUP PRD_GRID2 SET ATTRIBUTE ‘COMPATIBILITY.ASM’=’11.2’;

ALTER DISKGROUP PRD_GRID2 SET ATTRIBUTE ‘COMPATIBILITY.RDBMS’=’11.2’;

5. The commands will change the compatibility levels for the PRD_GRID2 diskgroup and the new values can be verified using the following query:

SQL> COL NAME FORMAT A12
SQL> COL COMPATIBILITY FORMAT A20
SQL> COL DATABASE_COMPATIBILITY FORMAT A20

SQL> SELECT NAME,COMPATIBILITY,DATABASE_COMPATIBILITY from v$asm_diskgroup; 

NAME         COMPATIBILITY        DATABASE_COMPATIBILI
------------ -------------------- --------------------
PRD_DATA     11.2.0.0.0           11.2.0.0.0
PRD_FRA      11.2.0.0.0           11.2.0.0.0
PRD_GRID1    11.2.0.0.0           11.2.0.0.0
PRD_GRID2    11.2.0.0.0           11.2.0.0.0 

6. Once the data has been verified, attempt to configure the diskgroup for OCR.   This configuration requires ‘root’ privileges. Connect to the server as root. and execute ocrconfig command from the $GRID_HOME/bin directory. 

[root@prddb3 bin]# ./ocrconfig -add +PRD_GRID2

7.  To verify if the new OCR file is created and the /etc/oracle/ocr.loc file is updated with the new file information.

[root@prddb3 bin]# cat /etc/oracle/ocr.loc
#Device/file  getting replaced by device +PRD_GRID2
ocrconfig_loc=+PRD_GRID1
ocrmirrorconfig_loc=+PRD_GRID2

8. The  ocrcheck command reflects two OCR locations

[root@prddb3 bin]# ./ocrcheck
Status of Oracle Cluster Registry is as follows :
         Version                  :          3
         Total space (kbytes)     :     262120
         Used space (kbytes)      :       3972
         Available space (kbytes) :     258148
         ID                       : 1288159793
         Device/File Name         : +PRD_GRID1
                                    Device/File integrity check succeeded
         Device/File Name         : +PRD_GRID2
                                    Device/File integrity check succeeded 

                                    Device/File not configured 

                                    Device/File not configured 

                                    Device/File not configured 

         Cluster registry integrity check succeeded 

         Logical corruption check succeeded 

9. Apart from the standard utilities used to very the integrity of the OCR file, the $GRID_HOME/log/prddb3/client directory also contains logs reflecting that the change was successful.

[root@prddb3 bin]# cat /app/grid/product/11.2.0/log/prddb3/client/ocrconfig_25560.log
Oracle Database 11g Clusterware Release 11.2.0.1.0 - Production Copyright 1996, 2009 Oracle. All rights reserved.
2010-07-10 21:01:00.652: [ OCRCONF][4224605712]ocrconfig starts...
2010-07-10 21:01:13.593: [ OCRCONF][4224605712]Successfully replaced OCR and set block 0
2010-07-10 21:01:13.593: [ OCRCONF][4224605712]Exiting [status=success]... 

10.  The clusterware alert log also has an entry indicating successful addition of the OCR disk.

/app/grid/product/11.2.0/log/prddb3/alertprddb3.log
[crsd(27512)]CRS-1007:The OCR/OCR mirror location was replaced by +PRD_GRID2.

11.   Lets check if the physical files can be found on the ASM storage.  Set the ORACLE_SID to the ASM instance on the server and using asmcmd the following can be found

ASMCMD> pwd
+PRD_GRID2/PRDCW/OCRFILE
ASMCMD> ls -lt
Type     Redund  Striped  Time             Sys  Name
OCRFILE  UNPROT  COARSE   JUL 10 21:00:00  Y    REGISTRY.255.715795989 

ASMCMD> cd +PRD_GRID1/PRDCW/OCRFILE
ASMCMD> ls -lt
Type     Redund  Striped  Time             Sys  Name
OCRFILE  UNPROT  COARSE   JUL 10 21:00:00  Y    REGISTRY.255.724021255 
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coexist 10gR2 and 11gR2 RAC db on the same cluster – Part II

I accidently posted this blog entry over my previous entry on this same topic.  Thanks to Google I was able retrieve my old post from the Google cache and posted it again to my blog.

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My previous post discussed about the various stumbling blocks we encountered during our 10gR2 database installation in a 11gR2 environment. We took it a step at a time to troubleshoot and install the database documenting and fixing the issues as we go. Yesterday browsing through Metalink I noticed a very recent article on the same subject.
Pre 11.2 Database Issues in 11gR2 Grid Infrastructure Environment [ID 948456.1]
Which recommends several patches and steps that could help ease the installation process