Starting in WAS 18.104.22.168 running on IBM JVMs, the default artifacts produced on an OutOfMemoryError have changed. In addition to the old defaults (first four OOMs create a PHD, javacore, and snapdump), a system dump will be produced on the first OOM: http://publib.boulder.ibm.com/infocenter/wasinfo/v8r0/topic/com.ibm.websphere.base.doc/info/aes/ae/ctrb_java626.html.
Some customers have become used to system dumps meaning crashes, so don't be worried. System dumps are a richer and alternative artifact to understand OOMs using the Memory Analyzer Tool and the IBM Extensions for Memory Analyzer.
For customers running *nix based operating systems, this is a good time to check your ulimits and make sure they're setup correctly, so that any system dumps produced are not truncated: AIX, Linux, i/OS, z/OS.
Update: TechNote describing this: http://www-01.ibm.com/support/docview.wss?uid=swg21584396.