Oc4j islands

Question

Hello all,
when I create few more islands other than juts one default_isalnd for my oc4j , the http requests to my application are being load-balanced automatically with all the available island processes.Is this the default behavior when I create more islands within a oc4j container?
If this is the case then why do i need creating clusters of oc4j's on different machines which host the same application so that my OHS will automatically load-balance with oc4j's on different machines in a cluster topology if I have got the option of creating more islands in my oc4j in my own single server,requests will anyways load-balanced among islands with my oc4j...
Plz help..i hv lil knowledge of oc4j and its islands..:)
Edited by: anandk on Nov 19, 2009 1:15 PM
Edited by: anandk on Nov 19, 2009 1:22 PM

Answer 1

Thanks for correcting that Roberto - I was confusing myself between versions there ;-)
anandk:
Yes, with 10.1.2 you had to specify which OC4J instances where handling which locations (context roots) in mod_oc4j.conf, e.g. in it's simplest form it might be:
<IfModule mod_oc4j.c>
Oc4jMount /app1/* app1
</IfModule>
(see [http://download.oracle.com/docs/cd/B14099_19/web.1012/b14007/confmods.htm#CIHJBGFB] )
With 10.1.3, you can still configure the routing statically if you want, but by default OC4J automatically registers its context roots with OHS/mod_oc4j via ONS
(see [http://download.oracle.com/docs/cd/B25221_04/web.1013/b25211/confmods.htm#CIHJBGFB] ).
On the wider point about JVMs etc, typically I would have different OC4J instances for the bigger applications to give me better control (e.g. restarting the container). For your example 10 applications, maybe only 2 or 3 of them are really important so would have their own OC4J instances and the remainder would be installed together in another instance. The number of JVMs per OC4J instance depends on the demands of the application but of course you need to consider how many other JVMs are running on the same server, how much physical memory there is available, how many cores you have, etc.