Forced node shutdown completed, restarting. Occured during startphase 0. Initiated by signal 11. (no replies)

NDB Server version: 5.6.29-ndb-7.4.11-cluster-commercial-advanced-log
Storage provisioned through Oracle VM
OS: RHEL 6.5

In an NDB cluster setup on a VM environment, we have configured management node, data node and sql node in a single node, with 2 servers in cluster.

NDB cluster data nodes, keep shutting with this message.
ndbmtd:12729 blocked for more than 120 seconds --- (error seen in dmesg output)

NDB cluster log says:

Forced node shutdown completed, restarting. Occured during startphase 0. Initiated by signal 11.

This has caused thrice in 2 days and no idea why its happening. Can someone help, what could be the reason for such abrupt shutdowns?

Thanks