It's all about the answers!

Ask a question

Insight: WAS MAX_HEAP_SIZE parameter?

Timur Markunin (6495165145) | asked Oct 10 '12, 9:29 a.m.
I'm wondering what are allowed values for MAX_HEAP_SIZE parameter of WAS7 (32-bit). We are using 768 and it works but when we changed it to 2048 it failed with:
JVMJ9VM015W initialization error for library j9gc24(2): Failed to instantiate heap; 2G requested Could not create the Java virtual machine.

-thanks in advance

Accepted answer

permanent link
Benjamin Silverman (4.1k610) | answered Oct 10 '12, 1:49 p.m.
Hi Timur,

You can take advantage of a larger heap setting if you are using a 64-bit OS and 64-bit install of WebSphere.  You should set the JVM heap no higher than 1/2 the total physical memory divided by the number of instances of WAS you are running.  For example, if your system has 8GB of RAM but is running 2 instances of WAS, you should set the max heap no higher than 2GB on each instance ((8GB/2)/2).  If you have 16GB on the system and only 1 instance of WAS running, you can set the max heap to 8GB.  There are lots of other aspects to consider when it comes to tuning WAS.  You may want to have a look at this article.  Hope it helps, 
Timur Markunin selected this answer as the correct answer

2 other answers

permanent link
Ali Manji (59147) | answered Oct 10 '12, 9:35 a.m.
Hi Timur -

For most environments, where RRDI/Insight is only application deployed to the WAS server, 1024 is the recommendation.


permanent link
Karl Weinert (2.0k52736) | answered Oct 10 '12, 10:12 a.m.
Seems to vary by the OS, OS version, jvm and what else is running on the system.

Searching for "Failed to instantiate heap; 2G requested Could not create the Java virtual machine" on Google I found a few hits. This one seems to have the best explanation (according to the up votes anyway)

1850 MB seemed to be one of the higher values that was successfully used on Windows.

Your answer

Register or to post your answer.

Dashboards and work items are no longer publicly available, so some links may be invalid. We now provide similar information through other means. Learn more here.