Our latest production issue: one morning our app kept crashing. Restart. Crash after some minutes. Out of memory.
It turned out to be a CLOB that was almost 2 GB big and got read when a user triggered a certain action. The 2 GB CLOB ended up in an almost 4 GB big char (because char is 16 bit in Java) and this was too much even for 8 GB heap space.
Of course that CLOB was not supposed to be that big!
It took some time to identify the root cause.