After a core dump, heap dump, or java dump is created, by default, the dump will reside in the ${WAS_INSTALL_ROOT}/profiles/your_profile directory. This usually is not perferred, as this can cause the profile directory to eventually run out of disk space.
You can specify a custom location for the core/heap/java dump files to be written to by creating the following environment entries. Refer to creating environment entries if you are not familiar with how to create environment entries.
You will need to restart the application server for this change to take effect.