[kdb_read_mem] no real storage @ FFFFFFFFFFF98B0
The reason is that kdb is trying to access virtual memory which was swapped to disk. AIX kernel core dump contains data in physical memory only. So for data structure in swap partition or swap file, kdb cannot address it correctly. That's why such error happened. The solution is to pin all kernel data structure and text segments so that they never are swapped to disk. If you encouter the error, that means you are not good luck and some kernel data strcuture were not pinned. No solution.
Good news for AIX version 7.1, it is a default setting and this problem won't happen.