Ever come across a stituation where you need to take a look at the heap dumps , as to whats eating up the memory ?
Well depends which version of JDK u r on. The couple I know of are:
Well depends which version of JDK u r on. The couple I know of are:
- jmap - a very old command which is now un supported . If u r using old versions of JDK prior to 1.5 this command is handy.
- jconsole - you can aquire the heap dump using the hotspotdiagnostics using the javax Mbeans. For jconsole to recognize the process , we should start the java process with the following :
-Dcom.sun.management.jmxremote.port=<PORT>
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false
- jrmc - jrockit mission control - If you are on the latest versions of JDK from jrockit , this is an ultra cool utility provided to be able to diagnose and monitor and profile your jvm. Go to the Advanced ->Diagnose->heapdumpprof util and generate the heap dump at the desired location.
- When you startup the jvm add the arguments -XX:+|-HeapDumpOnOutOfMemoryError and -XX:HeapDumpPath=<Location where the dump should be written to>
- Alternatively if you are using Jrockit you can provide the following startup arguments -Djrockit.oomdiagnostics=true and -Djrockit.oomdiagnostics.filename=d:\heapdump.log
- You could also monitor the memory using visualvm provided in latest jdks which give you better insight on the young heap and the old heap.
- Eclipse memory analyzer can also be used to generate a heap dump and also view the dum generated by any of the above processes. This is very helpful m when you want to identify memory leaks etc
The dump thus generated usually can is a log file which you can read or a hprof file which can be analysed using a memory analyzer(eclipse plugin http://www.eclipse.org/mat/downloads.php).
