The simple answer is RSCT (the "cluster" software) trace data from key daemons (sub-systems) like IBM.ConfigRM, cthags, cthats, and possibly even RMCd. IBM Support would use this trace data to confirm whether or not it was RSCT that forced the reboot, and if so, then why.
However what isn't always that simple is collecting these trace files before they wrap. The trace files for all the RSCT and TSAMP core daemons and Resource Managers are setup to be a fixed size and First-In, First Out (FIFO). Some of these... [More]