Instance Critical Process (SA00) died unexpectedly- Instance termination due to error 12752

Version:

Version:  12.1.0.2.0 - 64bit Production in Exadata (8-node RAC)

Issue:

RAC DB instance in 1 of 8 nodes not coming up. RAC DB instances are up and running in other 7 nodes.

Error:

Instance Critical Process (pid: 7, ospid: 72674, SA00) died unexpectedly
Time drifts can result in an unexpected behavior such as time-outs. Please check trace file for more details.
Mon Dec 29 00:52:01 2014
System state dump requested by (instance=2, osid=72660 (PMON)), summary=[abnormal instance termination].
Mon Dec 29 00:52:02 2014
PMON (ospid: 72660): terminating the instance due to error 12752

Reason:

The DB instance was crashing out on startup due to shared memory issues in that node.

The process which was failing was SA00 which is a new process from 12C. 
SAnn is SGA Allocator which allocates the  rest of the SGA  in small  chunks. Only a small fraction of SGA is allocated during instance startup. rest allocation is done by SAnn background process from 12c.

Fix:

Free or make more shared memory in the node for the instance and startup the instance.