After creating a domain with a cluster profile on a Linux system, you may encounter a java.lang.OutOfMemoryError: Java heap space error, and the server instance may fail to restart because the MQ broker does not start. The system never recovers after this condition. The problem is a misconfigured /etc/hosts file; specifically, the server host name is pointing to the loopback address 127.0.0.1.
By design, an MQ broker cluster cannot start with the network device configured to point to the loopback address. This is not a bug. The solution is to make sure that the /etc/hosts file for the Communications Server host does not point to 127.0.0.1.