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From "Ian H" <>
Subject Re: Error when increasing Tomcat's maximum memory pool
Date Tue, 08 May 2007 22:57:30 GMT
Thanks again, both Filip & Chuck,

Is this interpretation of the information out there correct:
- the maximum memory available for allocation for the pool will depend
on the amount of contiguous memory that's available to be allocated
- on a W2K box with 4GB of RAM, we will likely have, by default, 2GB
earmarked for the OS, and 2GB for applications (seriously cutting into
what would be contiguous and available for the pool)
- on W2K Enterprise or Datacenter editions, you could opt to start
with the /3GB switch and shift the allocation to 1GB/3GB for os/apps,
respectively, increasing the likelihood of more contiguous space being
available for the heap
[Regarding the /3GB switch not being recommended on W2K Standard
Edition: does anyone have direct experience with this configuration
and Tomcat as relates to stability, etc.?]

- given the hypothetical scenario that more contiguous space has
mysteriously been achieved for allocation (via choosing a different
hardware architecture or what have you) -- does Tomcat 5.5 still have
the 2GB limit I've heard mentioned?  Do newer versions still have this
limitation?  Are there any guidelines to go by regarding how much of a
tradeoff there will be for the extra burden related to garbage
collection with larger heaps, or is it a matter of "test and see"?

Thanks again,

- Ian

On 5/8/07, Filip Hanik - Dev Lists <> wrote:
> 32 bit limitations, the entire process heap is around 2GB, leaving you
> with the number you found for the java heap
> Filip
> Ian H wrote:
> > I have Tomcat 5.5 running on a Windows 2000 machine having 4GB of RAM
> > (recently upgraded from 2GB).  The JVM in place is 1.4.2_12.
> >
> > Using the "Configure tomcat" widget, I attempted to increase the
> > maximum memory pool from 1280MB that had been working to 2560MB.  At
> > this point, Tomcat fails to start, with these errors showing up in the
> > jakarta log:
> >
> >  JNI Error occurred during initialization of VM
> >  JNI Could not reserve enough space for object heap
> >
> > Googling around, I've only found that there seems to be a limit which
> > varies based on the flavour of the components in an installation,
> > typically ranging from around 1700MB to 2GB...I have yet to find
> > anything comprehensive detailing these limitations, however.
> >
> > That being said, with its current configuration, Tomcat will only
> > start on my system with the maximum pool capped at 1344MB...anything
> > higher than this and it fails.
> >
> > Does anyone have any suggestions regarding how to diagnose what's
> > limiting this, or suggestions for increasing it?
> >
> > Thank you very much,
> >
> > - Ian

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