To check to see if you need to delete JournalNodes, on the Ambari Server host:

curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X GET <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/host_components?HostRoles/component_name=JOURNALNODE

If this returns an empty items array, you can go on to Delete the Additional NameNode. Otherwise you must delete the JournalNodes.

To delete the JournalNodes, on the Ambari Server host:

curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X DELETE <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/hosts/<JOURNALNODE1_HOSTNAME>/host_components/JOURNALNODE curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X DELETE <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/hosts/<JOURNALNODE2_HOSTNAME>/host_components/JOURNALNODE
 curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X DELETE <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/hosts/<JOURNALNODE3_HOSTNAME>/host_components/JOURNALNODE

Verify that all the JournalNodes have been deleted. On the Ambari Server host:

curl -u <AMBARI_USER>:<AMBARI_PW> -H "X-Requested-By: ambari" -i -X GET <AMBARI_PROTO>://localhost:<AMBARI_PORT>/api/v1/clusters/<CLUSTER_NAME>/host_components?HostRoles/component_name=JOURNALNODE

This should return an empty items array.