JBoss crashed

The short answer is that JBoss cannot cause the crash, except very indirectly by finding a bug in the JVM.

You should have a core dump (probably in JBOSS_DIST/bin) that you can give to your JVM provider. Make sure you search their archive first to see whether it is already fixed or a known issue.

e.g. Sun's bug reports

Native code

If you are using native code (like Oracle OCI) check to see whether the problem is in the native code or the JVM. You should be able to determine this from the message at the top of the core dump.

Dump locations and OS Configuration

The "probably" above means the actual location is dependent on a number of things.

You need to consulate your JDK docs for the exact location it will try to use.

It would be more correct to say it will probably go in the "process work directory", the text above assumes that this is the JBoss binary directory. Which it will be if you did

$ cd JBOSS_DIST/bin

$ ./run.sh

It might not be if you started jboss from a different working directory, e.g. you are running jboss as a service and haven't explicitly set the $PWD environment variable (or whatever the mechanism is used for your OS).

NOTE: For the dump to work, the actual directory must be writable by the user running the process.

For real OS core dumps (rather than those produced by the JDK) you will likely have to change some shell parameters. e.g. on most linux distributions, the core dump size is set to zero for security reasons.

$ ulimit -a
core file size          (blocks, -c) 0

etc.