In this post, I will demonstrate three
methods to identify the oracle clusterware’s master node. Pls note that
clusterware master is different from Resource master in oracle database
instance. To know about how to find the resource master,
Importance of master
node in a cluster:
- Master node has the least Node-id in the cluster. Node-ids are assigned to the nodes in the same order as the nodes join the cluster. Hence, normally the node which joins the cluster first is the master node.
- Master node has the least Node-id in the cluster. Node-ids are assigned to the nodes in the same order as the nodes join the cluster. Hence, normally the node which joins the cluster first is the master node.
- CRSd
process on the Master node is responsible to initiate the OCR backup as per the backup policy
-
Master node is
also responsible to sync OCR cache across the nodes
-
CRSd process oth the master node reads from and writes to OCR on disk
- In
case of node eviction, The cluster is divided into two sub-clusters. The
sub-cluster containing fewer no. of nodes is evicetd. But, in case both the
sub-clusters have same no. of nodes, the sub-cluster having the master node
survives whereas the other sub-cluster is evicted.
Oracle ClusterWare master’s information can be found
- by scanning ocssd
logs from various nodes
- by scanning
crsd logs from various nodes.
- by identifying
the node which takes the backup of the OCR.
If master node gets evicted/rebooted,
another node becomes the master.
I have a 3 node setup. I check the ocssd logs on the 3 nodes for the string
‘master node’ and note that node 3 is the
master node.
[grid@host01 root]$ cat $ORACLE_HOME/log/host01/cssd/ocssd.log |grep ‘master node’ |tail -1
2012-11-23 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
2012-11-23 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
$ORACLE_HOME/log/host03/cssd/ocssd.log |grep ‘master node’ |tail -1
2012-11-23 10:14:37.001:
[ CSSD][778700688]clssgmCMReconfig: reconfiguration
successful, incarnation 248954981 with 3 nodes, local node number 3, master node number 3
If I take the OCR backup right now, it will be taken by
node3 (master node).
[root@host02 cssd]# ocrconfig -manualbackup
host03 2012/11/24
09:54:48 /u01/app/11.2.0/grid/cdata/cluster01/backup_20121124_095448.ocr
Let us check crsd logs of various
nodes, looking for the string OCR MASTER.Note that node3 is the master node
presently.
cat
/u01/app/11.2.0/grid/log/host01/crsd.log| grep -i 'ocr master'
[grid@host01 crsd]$ cat
/u01/app/11.2.0/grid/log/host01/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2012-11-23 10:15:01.403:
[ OCRMAS][2877356944]th_master: NEW OCR MASTER IS 3
[root@host02 crsd]# cat
/u01/app/11.2.0/grid/log/host02/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2012-11-23 10:15:03.561:
[ OCRMAS][876976016]th_master: NEW OCR MASTER IS 3
[root@host03 crsd]# cat
/u01/app/11.2.0/grid/log/host03/crsd/crsd.log |grep ‘OCR MASTER’ | tail -3
2012-11-23 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 mastership 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.
[grid@host01 root]$ cat
$ORACLE_HOME/log/host01/cssd/ocssd.log |grep ‘master node’ |tail -1
2012-11-24 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
$ORACLE_HOME/log/host02/cssd/ocssd.log
|grep ‘master node’ |tail -1
2012-11-24 10:09:23.502:
[ CSSD][778696592]clssgmCMReconfig: reconfiguration
successful, incarnation 248954982 with 2 nodes, local node number 2, master node number 1
As can be seen from ocssd logs of the
remaining two nodes, node1 has become the master now.
Now If I take the OCR backup, it is taken by node1 while earlier backups were
taken by node3 which was the then master.
[root@host02 cssd]# ocrconfig
-manualbackup
host01 2012/11/24
10:12:29 /u01/app/11.2.0/grid/cdata/cluster01/backup_20121124_101229.ocr
host03 2012/11/24
09:54:48 /u01/app/11.2.0/grid/cdata/cluster01/backup_20121124_095448.ocr
Let us check crsd logs of various nodes, looking for the
string OCR MASTER
[grid@host01 crsd]$ cat
/u01/app/11.2.0/grid/log/host01/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2012-11-24 10:08:45.884:
[ OCRMAS][877356944]th_master:13: I AM THE NEW OCR MASTER at
incar 47. Node Number 1
[root@host02 crsd]# cat
/u01/app/11.2.0/grid/log/host02/crsd/crsd.log
|grep ‘OCR MASTER’ | tail -1
2012-11-24 10:08:45.364:
[ OCRMAS][876976016]th_master: NEW OCR MASTER IS 1
[root@host03 crsd]# cat /u01/app/11.2.0/grid/log/host03/crsd/crsd.log |grep ‘OCR MASTER’ | tail -1
2012-11-24 10:12:20.282:
[ OCRMAS][877422480]th_master: NEW OCR MASTER IS 1
$ocrconfig
–showbackup
3rd
select
*from gv$gcs_resource;
1 comment:
Thanks Buddy,
You make very simple step to identify i am very much thankful ....
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