I know that it's possible to dump heap when an OutOfMemoryException
is occuring on this JVM but is it possible to ask a live dump with tools like jmap
or jconsole
?
You need to be aware that there are "system" dumps (basically OS core files) and "heap" aka portable heap dumps (PHD). The later ones are less usefull as they do not contain actual data. They are hower enabled by default.
On AIX or Linux Typically you will set up -Xdump:system
(short for -Xdump:system:events=gpf+user
) to allow kill -3 <pid>
to trigger a heap dump.
BTW, you can with the default options use kill -ABRT <pid>
. However this will terminate your JVM.
Run java -Xdump:what
to see your defaults, like:
> /usr/java6/bin/java -Xdump:what -version
Registered dump agents
----------------------
-Xdump:system:
events=gpf+abort+traceassert,
label=/home/u0002824/core.%Y%m%d.%H%M%S.%pid.%seq.dmp,
range=1..0,
priority=999,
request=serial
----------------------
...
java version "1.6.0"
Java(TM) SE Runtime Environment (build pap3260sr9fp2-20110627_03(SR9 FP2))
With turned on system dumps:
> /usr/java6/bin/java -Xdump:system -Xdump:what -version
Registered dump agents
----------------------
-Xdump:system:
events=gpf+user+abort+traceassert,
label=/home/u0002824/core.%Y%m%d.%H%M%S.%pid.%seq.dmp,
range=1..0,
priority=999,
request=serial
----------------------
-Xdump:heap:
events=systhrow,
filter=java/lang/OutOfMemoryError,
label=/home/u0002824/heapdump.%Y%m%d.%H%M%S.%pid.%seq.phd,
range=1..4,
priority=500,
request=exclusive+compact+prepwalk,
opts=PHD
----------------------
-Xdump:java:
events=gpf+user+abort+traceassert,
label=/home/u0002824/javacore.%Y%m%d.%H%M%S.%pid.%seq.txt,
range=1..0,
priority=400,
request=exclusive+preempt
----------------------
-Xdump:java:
events=systhrow,
filter=java/lang/OutOfMemoryError,
label=/home/u0002824/javacore.%Y%m%d.%H%M%S.%pid.%seq.txt,
range=1..4,
priority=400,
request=exclusive+preempt
----------------------
-Xdump:snap:
events=gpf+abort+traceassert,
label=/home/u0002824/Snap.%Y%m%d.%H%M%S.%pid.%seq.trc,
range=1..0,
priority=300,
request=serial
----------------------
-Xdump:snap:
events=systhrow,
filter=java/lang/OutOfMemoryError,
label=/home/u0002824/Snap.%Y%m%d.%H%M%S.%pid.%seq.trc,
range=1..4,
priority=300,
request=serial
----------------------
...
Do not forget to run jre/bin/jextract
on the core. * .dmp files.