The command stop-node-agent stops all the instances in the node. But this command is only supported in local mode. If you're in Unix/Linux environment, you may be able to use "ssh <user>@<hostname> "asadmin stop-node-agent".
[Message sent by forum member 'janey' (jane.young_at_sun.com)]
http://forums.java.net/jive/thread.jspa?messageID=363664