Large OPMN header vs. Small ORMI header.

Question

We are developing an application using OC4J. We used to just use a lightweight OC4J container with ORMI. The problem then was that each time the server was restarted; we had to adjust the port number our client used. I addition, creating new OC4J containers was a bit of a strain. Lately we have switch to a complete Oracle application server running multiple OC4J instances. This is much better as we now can just use the OC4J instance name in or URL and nor worry about ports. However, the OPMN protocol has a very large overhead: Sending a ping to our appserver using ORMI resulted in a 4Kb message, whereas the same ping using OPMN caused a 182Kb message! This is a problem for us, as some of our clients have very low bandwidth.
I won’t bother to post the OPMN message as it is over 5500 lines, but it starts like this:
MESSAGE
<!DOCTYPE pdml>
<pdml version=’9.0.4’ name=’opmn’ host=’myServer’ id=’8803’ timestamp=’1179144209761’>
<statistics>
Now, for every line in the message, a long series of XML strings are parsed. For instance, for every oc4j Instance, the same xml is processed, even though we define in our URL what instance to use. CPU time, up time, ports, hosts, protocols, states, heap, memory, pids, processes, message values, connect types, and so on are wrapped in this XML.
</statistics>
</pdml>
MESSAGE AGAIN
There is so much information wrapped in this message that it clogs down the line and is a major problem for us.
Is there a way to turn off all this overhead for the OPMN protocol? Can we easily use ORMI with a fixed port on an OC4J instance on an application server?

Answer 1

Geir,
What would be your specific requirements of administration/stability/logging/performance features to make it necessary to use OPMN?
If you conclude it is not necessary, you can still use the standalone OC4J container. As you may have already learned, it is through the rmi.xml file that you can set the port numbers for both ORMI/ORMIS services. Or, as a blog suggests, you can override those ports (for versions above 10.1.3) by passing them as agruments to the command line.
Regarding to your notes no the OPMN message sizes, it is perhaps due to the admin info it's due to carry since it is an admin protocol, not a transport one.
And to answer your last question, yes you can. Oracle presets a range of ports that are managed by the OPMN process; nevertheless, you can actually extract a couple of numbers from that range (by editing opmn.xml) and setting them as they fit your needs for your OC4J instances.
Rick B.