Hi,

I'm running:

IBM WebSphere Application Server, 6.0.0.1
Build Number: o0445.08
Build Date: 11/10/04

On a dual Xeon 3.2GHz server with 3.5GB RAM and MS Windows 2003 server. My q
uestion is- if an instance of WAS is running 2 J2EE applications with connec
tions to DB2 then what would a reasonable amount of RAM for its java.exe pro
cess to be using? At presen
t it is using a maximum of ~450mb which to me seems a fairly large amount gi
ven that the applications running on it are only being used in a test enviro
nment at present.

Anyone got any advice/configuration tips that could help this matter? Apolog
ies for this being a 'how long is a piece of string' question but we're a bi
t stumped here.

Thanks,

Mike

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Hi,

That is an open ended question.  It depends on many things, such as number o
f threads, number of connections, number of transactions, etc.

You should also upgrade to 6.0.2.x.

I would say that you need to do performance testing.

Brian

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michael_palfrey@natbrit.com wrote:
> Hi,
>
> I'm running:
>
> IBM WebSphere Application Server, 6.0.0.1
> Build Number: o0445.08
> Build Date: 11/10/04
>
> On a dual Xeon 3.2GHz server with 3.5GB RAM and MS Windows 2003 server. My questio
n is- if an instance of WAS is running 2 J2EE applications with connections to DB2 t
hen what would a reasonable amount of RAM for its java.exe process to be using? At p
res
ent it is using a maximum of ~450mb which to me seems a fairly large amount given that the a
pplications running on it are only being used in a test environment at present.
>
> Anyone got any advice/configuration tips that could help this matter? Apol
ogies for this being a 'how long is a piece of string' question but we're a 
bit stumped here.
>
> Thanks,
>
> Mike
>
>
>

Mike,
Standard answer #1: '42'.
Standard answer #2: get a Java profiling tool that will show what's
using memory. make sure to do this under load. It's possible that the
process has allocated that much memory but is not using it all.

Ken

[ Post a follow-up to this message ]

> Apologies for this being a 'how long is a piece of string' question

It's a good start that you realize it.

An absolute figure means nothing without the specific context of the
application and its needs.

A well written application can very well run with as few as 64 MB of heap,
while another (still well written) won't work with less than 1 GB.

As Ken pointed, you can profile and see what are the largest objects and if
they are not unduly allocated (static variables, collections, session
objects, caches, etc).

As a complementary measure, you can also activate verbosegc and review the
output with GCCollector, to see over time if it slowly grows or if it's a
temporary peak (the JVM won't release the native memory even when the heap
usage is going down -- it's not a bug, it's a feature).

[ Post a follow-up to this message ]

Shameless plug for ITCAM for Web Resources or ITCAM for WebSphere to
monitor the applications and WAS.

Ben_ wrote: 
>
> It's a good start that you realize it.
>
> An absolute figure means nothing without the specific context of the
> application and its needs.
>
> A well written application can very well run with as few as 64 MB of
> heap, while another (still well written) won't work with less than 1 GB.
>
> As Ken pointed, you can profile and see what are the largest objects and
> if they are not unduly allocated (static variables, collections, session
> objects, caches, etc).
>
> As a complementary measure, you can also activate verbosegc and review
> the output with GCCollector, to see over time if it slowly grows or if
> it's a temporary peak (the JVM won't release the native memory even when
> the heap usage is going down -- it's not a bug, it's a feature).

--
Jim Palistrant
IBM Tivoli WW Technical Evangelist/Enablement - ITCAM

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Hi Mike!
What are your -Xms and -Xmx settings?. If you have provided 1GB of Memory to
 start with, there is NO reason for JVM to crank up a FULL Garbage Collectio
n till it really thinks it's necessary (which will happen only when you are 
in the vicinity of shortage
of memory).

So, if you have a strong feeling that your App should not be consuming this 
much memory, try giving it 256 MB and see if it runs out of memory.

However, a through diagnosis can only be made by a profiling tool like jprob
e.

Best Regards,
- Karun

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