SQL> select instance_name,status from gv$instance;
INSTANCE_NAME    STATUS
node01          OPEN
node02          OPEN
node04          MOUNTED
node03          MOUNTED

~$ srvctl status database -d cldb -v
Instance node01 is running on node srv-n01. Instance status: Open,Readonly.
Instance node02 is running on node srv-n02. Instance status: Open,Readonly.
Instance node03 is running on node srv-n03. Instance status: Mounted (Closed).
Instance node04 is running on node srv-n04. Instance status: Mounted (Closed).