After a near-panic and interminable spin, it proved impossible to get useful diagnostic information. Here are some tools and techniques which should still be useful.
Handling of kernel panics shows a series of fundamental flaws in El Capitan, which can occur on any Mac.
Was that crash a freeze, a panic, or just a spinning beachball? And what do they mean?
For the last 15 weeks, this iMac has been freezing sporadically. I have run out of ideas, and hope that 10.11.6 fixes the bug.
I may at last have found a way to reduce the frequency of freezing in OS X 10.11.4 and later.
After another system freeze, it is clear the problems in El Capitan are not fixed in 10.11.5.
Has your Mac been freezing occasionally since updating to OS X 10.11.4? You are not alone, it seems.