ALERT: DB corruption after 12c upgrade for compressed tables during recovery

Did you compress tables on 11g before going to 12c?  If so, you need to check out My Oracle Support article "ALERT Bug 21682261 Corruption during Recovery after upgrading to 12c for Compressed Tables" from document ID 2058461.1 because you can run into corrupted tables if you need to recover them!  This is the worst possible news for a database because it violates all of the ACID principles and if you get to the recovery stage you already have your data in question!

ALERT: ORA-600 on Standby after switchover

I have been told that SCNs and ITLs are some sacred parts of the ACID test for transactions, but article "ALERT Description and fix for Bug 8895202: ORA-1555 / ORA-600 [ktbdchk1: bad dscn] ORA-600 [2663] in Physical Standby after switchover" found via document ID 1608167.1 on My Oracle Support gives us reasons that both SCNs and ITLs can be violated!