CAUSE
The issue has been investigated in the unpublished
Bug 9093161 -  GETTING ORA-600 [723], [105312] WHILE SHUTTING DOWN DB
closed as a duplicate of unpublished
Bug 8676674 -  ARCH REPORTED ORA-00600:[723] DURING SWITCHOVER


SOLUTION
There is no patch available for 8676674 on 11.2.0.1, but this has been fixed in the 11.2.0.2 patchset


Please refer to
Note 1179583.1 -  11.2.0.2 Patch Set - List of Bug Fixes by Problem Type


If possible, apply the latest patch-set (11.2.0.3 or 11.2.0.4) where the issue is fixed.




Workaround:


Set the following in init.ora for example to disable space leaks less than 9000 bytes:


event = "10262 trace name context forever, level 9000"
and stop and restart the database.