how much memory is needed for a heap dump ?

kohlerm · Post by **kohlerm** » Tue Nov 29, 2005 3:12 pm

Hi,
I frequently get crashes, when trying to do a heap dump for our application.
My guess is that the problem is that there is not enough memory available for the JVM.

We are typically running with a heap size of 1024Mbyte on Windows 32 bit and JDK 1.4.2.

Is there a maximum heap size that is known to work ?+

Regards,
Markus

Post by **Anton Katilin** » Thu Dec 01, 2005 10:44 am

Hi,

What kind of crashes do you experience?
Are there any crash logs or error messages?

Java 1.4 by its design is not capable to create dumps of heaps with sizes bigger that 1G (approximately).

So if the Java crashes because of this limitation, there are only the following workarounds:

- reduce -Xmx to e.g. 700M. I cannot tell the exact number, because the actual limit may depend on kinds of objects that are in the heap at the moment of dumping.

or

- profile under Java 5.0, which doesn't have this limitation

Best regards,
Anton