The more you understand...
The less you have to memorize. Been a while since I linked back to Kathy Sierra, but her posting on "How to get users to RTFM" had a graphic I really liked (take a second to click the link, it is right on top).
Many people presume I have "memorized all there is to memorize" about Oracle (or "much that there is to memorize"). Not true - I hit the manuals every day, every single day. To look up esoteric syntax, to get a clarification, to refine my understanding of how something works. It is less rote memorization than it is understanding of the fundamentals. I can look at a proposed trigger and in a couple of minutes explain why it won't work in real life (you'd be surprised how many don't - triggers used to enforce integrity constraints most times have multi-user logic flaws). It is not because I've memorized 100 use cases - rather that I understand the concepts in the database (multi-versioning, non-blocking reads and what they mean to us and why we care).
Anyway, read her post (it is a long one) - I think she makes a good point. I liked the classification of the types of reading material necessary for a product - I think I do mostly #3 and #4 - #3 in the books and #4 on asktom.