Which rac node is the master node

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.
- 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.

1. Check which node is taking OCR backup  .

[root@node1 ~]# /data01/app/11204/grid_11204/bin/ocrconfig  -manualbackup

node2     2015/04/28 12:05:53     /data01/app/11204/grid_11204/cdata/node-cluster/backup_20150428_120553.ocr

2, Scan the logs for crsd.log

[grid@node2 crsd]$ cat $GRID_HOME/log/node2/crsd.log | grep -i "New master"  | tail -2
2015-04-28 10:34:31.625: [   CRSSE][1272964864]{2:23089:2} Master Change Event; New Master Node ID:2 This Node's ID:2
2015-04-28 10:34:46.096: [UiServer][1272964864]{2:23089:2} Master change notification has received. New master: 2