I was wondering what a full node stores. I'm asking this because in an earlier question about the possibility of a double spend in IOTA this article was posted as an answer: http://www.tangleblog.com/2017/07/10/is-double-spending-possible-with-iota/
In this article, it is said that each node only knows a small part of the Tangle and therefore it's hard to perform a double spend. A malicious node has to both gain an overview of the whole Tangle (gain omnipresence, which is said to be hard) and perform PoW. These two combined make a double spend hard.
In another question I've asked about transaction verification (both on slack and here) it is said that a full node stores all transactions and therefore has a(n) (almost) complete overview of the Tangle. This is needed to do the verification of a transaction, which makes sense.
These two arguments seem to contradict each other. In other words, if nodes store the whole Tangle, it makes it easier to perform a double spend. If nodes only store a part of the Tangle, it makes it hard to do transaction verification.