Core dump instructions - Hung threads in WebSphere

Setting generic JVM arguments in WebSphere Application Server
http://www-01.ibm.com/support/docview.wss?rs=180&uid=swg21417365 Show archive.org snapshot

ARGUMENT:
-Xdump:system:events=user,request=prepwalk+compact+exclusive

To alter the location of the core dumps, you can either edit the -Xdump argument, or you can alter this environment variable

IBM_COREDIR=/path/to/where/dump/files/will/be/located

Setting environment entries in WebSphere Application Server
http://www-01.ibm.com/support/docview.wss?rs=180&uid=swg21254153 Show archive.org snapshot

SETTING UP FULL CORE DUMPS
Your ulimits are already set to unlimited, so the next thing to check is if SMIT has full cores configured. The instructions are below and also can be found in this technote in step 1:

"Crash on AIX produces no core or a truncated core"
http://www-01.ibm.com/support/docview.wss?rs=180&uid=swg21052642 Show archive.org snapshot

AIX
You must apply the ulimit settings above and also set the following SMIT settings on AIX:

CopyStart smit by typing "smit" as root
Go to System Environments -> Change/Show Characteristics of Operating System
Set the Enable full CORE dump option to TRUE
Ensure that the Use pre-430 style CORE dump option is set to FALSE
This can also be done by running

chdev -l sys0 -a fullcore='true' -a pre430core='false' as root

And can be checked with

$ lsattr -D -c sys -a fullcore -H

which should produce output similar to this:-

attribute deflt description user_settable

fullcore false Enable full CORE dump True

If a dump is not produced by the JVM, the gencore utility can be used to force a coredump.

JEXTRACT
To run jextract on the core dump, run this command:
<WAS_HOME>/java/jre/bin/jextract -J-Xcompressedrefs CORE_PATH

It will produce a zip file containing the core dump and libraries.

You can still capture javacores and server logs as done before. However be aware that aixperf.sh may still cause a core dump when tprof is run. You may want to either disable this command in the script, or lower the amount of time it runs (it runs for 60 seconds by default, I'd say lower it to 20).