Oracle AS - Clustering and remove clustering for AS1013

Enable Clustering
Reference: http://www.oracle.com/technology/products/ias/hi_av/Dynamic%20Routing.htm

In AS1013 we do not need to explicitly select multiple nodes via EM to join them into a cluster. However we configure a broadcasting address to opmn.xml of different nodes, different nodes will discover each other automatically and join as a cluster.

E.g. Running the following command for each node.
$ opmnctl config topology update discover "*225.0.0.20:8001"
$ opmnctl reload

The above command will update AS1013/opmn/conf/opmn.xml file with the following entry:

<topology>
<discover list="*225.0.0.20:8001">
</topology>

To see the cluster status in terminal,
$ opmnctl @cluster status -l

To see the individual application status,
$ opmnctl status -l -app

To see more usage of opmnctl command,
$ opmnctl usage config

When you login EM, at some point it will prompt you that only 1 EM should exist to rule the rest of AS instances.

Remove Clustering
To remove the instance from cluster, we'll execute the following command in that instance.
$ opmnctl config topology delete discover "*225.0.0.20:8001"
$ opmnctl reload
(Note: obtain the discover broadcasting value from AS1013/opmn/conf/opmn.xml)

Immediately it'll be out from the cluster.

As a stand-alone instance, it'll need to have EM running so that we can manage it easily. To explicitly startup EM, execute the following:
$ opmnctl startproc ias-component=OC4J application=ascontrol