In 3 node RAC setup,In initial stage--node 3 is the master node.
[oracle@host01 ~]$ cat $ORACLE_HOME/log/host01/cssd/ocssd.log |grep ‘master node’ |tail -1
2016-09-24 10:14:36.949: [ CSSD][2778696592]clssgmCMReconfig: reconfiguration successful, incarnation 248954981 with 3 nodes, local node number 1, master node number 3
[root@host02 cssd]# cat $ORACLE_HOME/log/host02/cssd/ocssd.log |grep ‘master node’ |tail -1
2016-09-24 10:14:36.953: [ CSSD][778696592]clssgmCMReconfig: reconfiguration successful, incarnation 248954981 with 3 nodes, local node number 2, master node number 3
[root@host03 ~]# cat $ORACLE_HOME/log/host03/cssd/ocssd.log |grep ‘master node’ |tail -1
2016-09-24 10:14:37.001: [ CSSD][778700688]clssgmCMReconfig: reconfiguration successful, incarnation 248954981 with 3 nodes, local node number 3, master node number 3
If I take the OCR backup right now, it will be taken by node3 (master node).
[root@host02 cssd]# ocrconfig -manualbackup
HOST3
2016/09/24 09:54:48 /u01/app/11.2.0/oracle/cdata/cluster01/backup_095448.ocr
Let us check crsd logs of various nodes, looking for the string OCR MASTER.Note that node3 is the master node presently.
[oracle@host01 crsd]$ cat /u01/app/11.2.0/oracle/log/host01/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2016-09-24 10:15:01.403: [ OCRMAS][2877356944]th_master: NEW OCR MASTER IS 3
[root@host02 crsd]# cat /u01/app/11.2.0/oracle/log/host02/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2016-09-24 10:15:03.561: [ OCRMAS][876976016]th_master: NEW OCR MASTER IS 3
[root@host03 crsd]# cat /u01/app/11.2.0/oracle/log/host03/crsd/crsd.log |grep ‘OCR MASTER’ | tail -3
2016/09/24 10:11:18.499: [ OCRMAS][877467536]th_master:13: I AM THE NEW OCR MASTER at incar 44. Node Number 3
Let me reboot node3 and check which node is assigned the master node now.
[root@host03 ~]# init 6
check the ocssd logs on the remaining two nodes (node1 and node2) for the string ‘master node’ and note that node 1 is the master node.
[oracle@host01 root]$ cat $ORACLE_HOME/log/host01/cssd/ocssd.log |grep ‘master node’ |tail -1
2016/09/24 10:09:23.522: [ CSSD][2778696592]clssgmCMReconfig: reconfiguration successful, incarnation 248954982 with 2 nodes, local node number 1, master node number 1
[root@host02 cssd]# cat $ORACLE_HOME/log/host02/cssd/ocssd.log |grep ‘master node’ |tail -1
2016/09/24 10:09:23.502: [ CSSD][778696592]clssgmCMReconfig: reconfiguration successful, incarnation 248954982 with 2 nodes, local node number 2, master node number 1
As can be seen from ocssd logs of the remaining two nodes, node1 has become the master now.
Now If I take the OCR backup, it is taken by node1 while earlier backups were taken by node3 which was the then master.
[root@host02 cssd]# ocrconfig -showbackup
host03 2016/09/24 09:54:48 /u01/app/11.2.0/oracle/cdata/cluster01/backup_095448.ocr
[root@host02 cssd]# ocrconfig -manualbackup
host01 2016/09/24 10:12:29 /u01/app/11.2.0/oracle/cdata/cluster01/backup_101229.ocr
host03 2016/09/24 09:54:48 /u01/app/11.2.0/oracle/cdata/cluster01/backup_095448.ocr
Let us check crsd logs of various nodes, looking for the string OCR MASTER
[oracle@host01 crsd]$ cat /u01/app/11.2.0/oracle/log/host01/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2016-09-24 10:08:45.884: [ OCRMAS][877356944]th_master:13: NEW OCR MASTER IS 1
[root@host02 crsd]# cat /u01/app/11.2.0/oracle/log/host02/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2016-09-24 10:08:45.364: [ OCRMAS][876976016]th_master: NEW OCR MASTER IS 1
[root@host03 crsd]# cat /u01/app/11.2.0/oracle/log/host03/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2016-09-24 10:12:20.282: [ OCRMAS][877422480]th_master: NEW OCR MASTER IS 1