Multiple JVM's in one JDK

Hi,
I am curious to know if one JDK spawning multiple JVM's cause any memory/performance issues. The reason being, my company is planning to have number of applications running in one Weblogic Server instance with Multiple JVM's spawning out of same JDK.
Please let me know if this is possible and if there are any negative effects of following this approach.
Any help is greatly Appreciated.
Thanks

JDK installation is a just binary. There is not limit on creating number of JVM runtime process.
There should not be negative effect assuming you have enough capacity on hardware box.

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Multiple JVM in one server

Hi,
Can we run multiple JVM's on one Solaris server with different applications configured for different JVM's or may be configure a memory intensive application to multiple JVM's.
Please let me know if this works and if there is any documentation for this.
Any help is greatly appreciated.
Thanks

Pione J wrote:
Can we allocate multiple JVM's to one application and i would really appreciate if you can provide me with some literature/suggestions as to how we can do this in Weblogic.Sure, it's called clustering and documentation is available here
http://e-docs.bea.com/wls/docs81/cluster/overview.html
Cheers,
Gerald

Multiple JVMs foe One WL6.1 instance

Hi,
Is it possible to attach multiple JVMs to an instance of WLS6.1
so that all JVMs will be self sufficient in serving client requests....
If it is possible then any pointers in that direction..???
regards
aseem

Each WL server runs in one JVM. If you want to have 4 JVMs, then run 4 WL
servers in one cluster.
"Aseem Rastogi" <[email protected]> wrote in message
news:[email protected]..
currently our App runs on 2 Iplanet App Server ( they are in Cluster)
and each App server has 2 VMs so we we are getting the feel of 4independent
App Servers but Physically we are able to get away with only 2 boxes.
We want to achive the same thing in Weblogic...
thanx
aseem
Michael Reiche wrote:
1) What is your requirement?
2) Clustering.
"Aseem Rastogi" <[email protected]> wrote in message
news:[email protected]..
Hi,
Is it possible to attach multiple JVMs to an instance of WLS6.1
so that all JVMs will be self sufficient in serving client
requests....
>>>
If it is possible then any pointers in that direction..???
regards
aseem

Ensuring one singleton instance for multiple JVMs

i am creating a singleton object. But singleton is per JVM (or rather per classloader) right? But i want to ensure only one instance of my singleton even if there are multiple jvms....how can i achieve that?

javanewbie80 wrote:
i am creating a singleton object. But singleton is per JVM (or rather per classloader) right? But i want to ensure only one instance of my singleton even if there are multiple jvms....how can i achieve that?You can't.
Given computers A and B. Neither have any connectivity by any means to the other.
Install the application on both and run it. There is no way for either application to know about the other thus only one of the following is possible.
1. Both applications run and create an instance. Then there are two instances and thus it fails.
2 The application refuses to run. Then there are none and thus it fails
Other solutions are possible given that some reasonable requirements based on actual business driven needs are presented.

JVM 1.3.1_06 Solaris 8 (sparc) multiple jvm's crash at the same time

Hi All,
I had multiple jvms crash all at the same time today morning, i was wondering if anyone had any similar issues with 1.3.1_06:
Only a few jvms left an hs_errpid.log: here is the one with the most info:
An unexpected exception has been detected in native code outside the VM.
Unexpected Signal : 10 occurred at PC=0xff02f8f8
Function name=VerifyClassCodes
Library=/www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/libjava.so
Current Java thread:
at java.lang.Shutdown.halt(Native Method)
at java.lang.Shutdown.exit(Shutdown.java:209)
at java.lang.Terminator$1.handle(Terminator.java:33)
at sun.misc.Signal$1.run(Signal.java:193)
at java.lang.Thread.run(Thread.java:479)
Dynamic libraries:
0x10000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/bin/../bin/sparc/native_threads/java
0xff350000 /usr/lib/libthread.so.1
0xff340000 /usr/lib/libdl.so.1
0xff200000 /usr/lib/libc.so.1
0xff330000 /usr/platform/SUNW,Ultra-Enterprise/lib/libc_psr.so.1
0xfe400000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/hotspot/libjvm.so
0xff2d0000 /usr/lib/libCrun.so.1
0xff1e0000 /usr/lib/libsocket.so.1
0xff100000 /usr/lib/libnsl.so.1
0xff0d0000 /usr/lib/libm.so.1
0xff1c0000 /usr/lib/libmp.so.2
0xff090000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/native_threads/libhpi.so
0xff060000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/libverify.so
0xff020000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/libjava.so
0xfe7d0000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/libzip.so
0xfe3e0000 /usr/lib/locale/en_US.ISO8859-1/en_US.ISO8859-1.so.2
0xfe390000 /www/gmgwh/weblogic/jdk/j2sdk1_3_1_06/jre/lib/sparc/libnet.so
0xfe230000 /usr/lib/nss_files.so.1
0xfe160000 /www/gmgwh/weblogic/6.1/sp4/lib/solaris/libmuxer.so
0xfd0e0000 /usr/ucblib/libucb.so.1
0xfd090000 /usr/lib/libresolv.so.2
0xfd050000 /usr/lib/libelf.so.1
0xfafd0000 /app/oracle/product/8.1.7.4/lib/libocijdbc8.so
0xe1800000 /app/oracle/product/8.1.7.4/lib/libclntsh.so.8.0
0xfafb0000 /app/oracle/product/8.1.7.4/lib/libwtc8.so
0xfaf90000 /usr/lib/libsched.so.1
0xfaee0000 /usr/lib/libaio.so.1
Local Time = Wed Jan 19 09:09:31 2005
Elapsed Time = 22367
# The exception above was detected in native code outside the VM
# Java VM: Java HotSpot(TM) Client VM (1.3.1_06-b01 mixed mode)
#

hi there
i would direct my efforts to search for the culprit on who generated the signal (either a INT, TERM or HUP). The crash occurred is just but another side-effect. The VM received a shutdown signal and shld exit. Just that while exiting, it crashed.
There is this bug
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4904881
Which is pretty rare. I am not sure if you are encountering this bug but if u have a core, a pstack of the core should show > 2 threads with doing the signal shutdown.

Multiple JVMs

Hi,
Can I run multiple JVMs on the same machie.
If I can, then what are the repurcussions of this.
Spark

I am happily using several JVM's on my Linux box:
1.1.8
1.2.2
1.3.1
1.4.1
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Server, Multiple JVMs sources

Hi,
i've to create a (web serivce) server application. This application should be ready for clustering or something, if one server isn't fast enough.
I know already some things abou concurrency in Java. I'm no Java newbie. But i don't know how clustering works.
Does it depend on the used JVM?
Or is this for every server (i.e. Tomcat, JBOSS, ...) different?
What are the requirements in the webservice-layer and in the persistance layer?
Any good internet pages/PDFs which discusses this?
Any good books?
I really hope some can help me here, because it's very important for me.
Cheers,
Ingo

I just re-read the guidelines for a clustered web app over the weekend, so I think I've got things straight. Your application will have to be sensitive to two important issues:
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2) The HttpSession object for a given session can only be in existence on one JVM at a time. If the HttpSession needs to migrate to another JVM, then it will be serialized and sent to the other JVM. As a result, adding an object to a session that is not Serializable may result in IllegalArgumentException being thrown. I'm guessing that in the case of a fail-over (node dies unexepectedly) that the HttpSession object is lost.
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Load balancing HTTP requests for an OC4J instance w/multiple JVMs

Hello everyone,
I am using OAS 10.1.3.1 and wish to load balance HTTP requests across an OC4J group of one or more OC4J instances, where each like named OC4J instance may have multiple JVMs or it may just have one JVM.
My mod_oc4j.conf file would contain the following directives :
Oc4jSelectMethod roundrobin:local
Oc4jRoutingMode Static
Oc4JMount /xyz/* xyz
In the degenerate case, I would like to have an OC4J group with a cluster size of one, and have that one OC4J instance have two or more JVMs. I would like to be able to receive a request within my web application, determine that the JVM that has been sent the request is the wrong JVM to process the request, and then call HttpServletResponse.sendRedirect("/xyz"). Then, when the browser receives the HTTP 302 response and issues the subsequent HTTP request, have that request sent to a different JVM than the previous JVM that issued the sendRedirect().
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In the full blown case, I would have an OC4J group with a cluster size > 1, and each of those OC4J instances would have at least one JVM. In that case, I wish the sendRedirect() call to allow the subsequent request to be sent to any one of the OC4J instances in the group, and any one of those JVMs within all of those OC4J instances.
Can anyone verify that my mod_oc4j mount directive is appropriate given the select method and routing mode? What else might I need to do to have a chance to have a different JVM respond to the request that results from a sendRedirect()?
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I should clarify that in the full blown environment, the OC4J instances that form a group will each be housed within a separate OAS instance that resides on its own machine.
So ideally, a request could be inbound to say OAS instance 1 on machine A, OC4J instance AA, JVM 2, and I need to force a redirect so that the request can actually be serviced by OAS instance 3 on machine C, OC4J instance AA, JVM 1, and I need to be able to call sendRedirect() against an HttpServletResponse from within a JVM until the subsequent request from the browser, Internet Explorer in my case, is serviced by that JVM.
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Multiple JVM instances

Dear all,
I am trying to create multiple JVM instances using createJavaVM(...) but I can't do it. When I try to create the second instance, the function returns an error.
Does anybody know about getting multiple JVM instances running??
Thanks in advance,

Hallo,
createJavaVM(...) trys to create a JVM in your current
process, so I am not surprised that you get an error
the second time round, because there is already a JVM
in the process. If you want multiple JVMs, each needs
to be in its own process.
Why do you want to create more than one JVM in your
process? The JVM is multithreadable, and you can start
more than one thread in the JVM. Would that do what
you want?I need multiple instances because my application needs nearly 2Gb of memory and the maximum heap I get is 1700 Mb. I think with multiple instances, I'll get it.
Do you know about getting a bigger heap??
>
David Singleton
[email protected]

Running Multiple JVM's on same Server has OutOfMemory - PermGen Errors

I have a scenario where I have 2 application servers. One is running one JVM and the other is running multiple JVMs.
Both are configured with:
-XX:+UseConcMarkSweepGC
-XX:+UseParNewGC
-XX:MaxPermSize=256m
-XX:+CMSPermGenSweepingEnabled
-XX:+CMSClassUnloadingEnabled
The server that is running with only 1 JVM runs stable, however the server that is running multiple JVMs has frequent crashes due to OutOfMemory - PermGen errors. The only other difference is the Heap size. 512mb for each JVM on the app server with multiple instances and 1GB for the server with 1 instance. Is there a relationship/settings that need to be tuned when running multiple JVM's on the same server to avoid this?
Thx

The only other difference is the Heap size. 512mb for each JVM on the app server with multiple instances and 1GB for the server with 1 instance.This isn't a trivial difference. Basically you're saying "When I give the server 1 GB then it's okay but when I give it 512 MB it's not okay." If I saw those symptoms I would take them at face value to start with.
So, turn off one of those servers on the machine that has two. Don't change anything else. Testable prediction: That won't fix your problem.

Multiple JVMs - What does it mean

Hello,
I was trying to understand this for quite a while. Googling around just obscured the use of the term.
Could you please tell me what does it mean when I hear someone say :
"This machine has multiple JVMs....." and ofcourse, how you can bring up just one amongst the many JVMs (by locally doing something or remotely instantiating it ) existing and running code there,
How can I setup multiple JVMs on my desktop ?
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Java HotSpot(TM) Client VM (build 1.3.1_19-b03, mixed mode)
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Singletons across multiple JVMs

I have an EJB application container which is spread across multiple JVMs(something like a clustered EJB container). I am using a Singleton class to hand out 'running serial numbers'. Therefore there is a Singleton class per JVM(which is not very clean but i chose this path in the absence of anything better). Each singleton comes up when it is first invoked within a JVM and reads a starting running number and a pool of numbers from the database. This way multiple Singletons will not step on each other when doling out the serial numbers and there is no need to go back to the database for every request to the 'running serial number'.
Is there some way to do some of the initialization within these Singleton's just ONCE across the multiple instances of the JVM ie. a real Singleton across multiple JVMs?
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Pranav,
thanks for your suggestions.
the idea of using a Session bean to access a serialized object was one of my design options when i first implemented this, but then i decided against it because of the overhead of having to make an RMI call for every request to the 'running serial number'. The application being written is for a performance benchmark, and the request to the number being done at least once for every transaction, I chose to use Singletons.
It is a clustered EJB container(not like most conatiners), in the sense that a single container is spread across multiple JVMs.
Now if your application is getting clustured
then you have a problem, in that what you can do is
what object you have made put it in JNDI context and
everytime you want to edit it pull it out edit and set
it back. This will act a your singleton object in
clustured environment accross JVM'sI did not fully understand the second part of your solution????
Ramdas

Running multiple JVM's using JNI

I am having problems starting multiple JVM's in our C++ application which is multi-threaded.
Iam able to start one JVM but when I attempt to start the second JVM in a new thread it fails with
the error of -5. This error states that a JVM is already running.
Help!

You can run more than one process that needs JVM using the AttachThread, DetachThread and GetCreatedJavaVMs calls.
First determine to see if you have a JVM -- using GetCreatedJavaVMs. Check if you can get the environment pointer (GetEnv call). Then try AttachThread. Once you are done, do a DetachThread.
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Regards,
Satish

Multiple JVM

Hi All
Can I run Weblogic server with multiple JVMs . I do do not mean here Sun JVM and Jrocket but I mean for example instead of 1 Sun JVM , Can I increase the processes to 3 or 4 JVM. In the old ORacle App Server we can use mutiple JVM by assigning by increasing the number of processes in opmn.xml . Can we do the same thing in Weblogic server ?
Thanks

Not to my knowledge. It is also not really good practice to use multiple JVM's.
This is due to the replication of data between separate JVM's (the one JVM
has to know what the other was doing when it crashes). This will become
a performance issue if you have large amounts of data which gets replicated.

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