Need answers on what C-Runtime heap is

Posted on 2009-05-18
Last Modified: 2013-11-23
We recently did an upgrade to DB2 and even more recently OnDemand (an IBM image archive app) on our AIX box and now we're having huge problems running an application.  We are trying to configure JProbe to help, but in the meantime I'd like more information on the error.  The error is the following:

JVMCL052 - Cannot allocate memory in initializeHeap for heap segment

From my understanding, this is NOT the java heap.  Read these comments below:

"The C-runtime heap of the process (not the Java object heap) is full. Increase the heap if that is possible in your environment. In a shared classes environment, see the shared classes User Guide for options that control shared memory, because the storage is managed by the JVM in this case."

The app is being ran on AIX version 5.3.  I don't know what C-runtime heap is or how to increase it.  I'm not the AIX administrator and my request has fallen on deaf ears.  This app ran much smoother in the past, so I know something with the OnDemand or DB2 upgrade has leached the AIX resources.  

Can someone help??
Question by:jackjeckyl
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LVL 62

Expert Comment

ID: 24419436
This is JVM error (not able) allocating data pages from system.

Author Comment

ID: 24426897
So what do I do?
LVL 62

Accepted Solution

gheist earned 25 total points
ID: 24429241
check ulimit -a
then use smitty to increase allowed (data ?) size to -1 or something less.
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LVL 68

Assisted Solution

woolmilkporc earned 25 total points
ID: 24464805
Might be that your Java heap is too big, so that no C heap is left for non-java-heap purposes (internal JVM functions etc.) Try to reduce it (-Xmx ... option)

Author Comment

ID: 24519009
gheist - everything is set to unlimited, except stack (32768), coredump (2048) and nofiles (2000).  Does any of that need to be changed.

woolmilkporc - I'll try reducing the java heap, although this was set low to begin with when I had these problems.  
LVL 62

Expert Comment

ID: 24520100
Yes - it uses stack extensively.

Author Comment

ID: 24522004
woolmilkporc - Your suggestion worked, somewhat.  I lowered it, and now it seems to be running better on the bigger jobs the application encounters.  However, I do get java heap errors sporadically.  I went from 2GB to 1.5GB.  Maybe I'll bump it to 1.75GB and see what happens.  

gheist - Increase the stack to what value?  I'm AIX illiterate, so if I suggest something to the AIX admins, I need to tell them what and how come.  
LVL 62

Expert Comment

ID: 24524852
I suggest doubling.
Might be you hit 13x256MB limit - patching java with ML package is known to help. Also thruput GC is better.

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