Is There An Unwritten Rule Against Using A Database

It is not a matter of me liking it or not. The OP asked about the rules, and I am pointing out that you are ignorant of the rules, and answered the OP incorrectly. Sorry you don't like the rules.

htdavidht, you have played more than 50 online games during the last 3 years and not even once you cared to look up the rules?

jimmy, the question is about unwritten rules. sred, for me it is a waste of time, more like reading the TOS. however I have being wondering why so big difference on my normal and 360 scores, this explain it, they are not more dedicated than me on studying opening theory, they just pull out half their games from a database.

This one's a written rule (and yes, it's in the TOS -- something we should all have read when we created our accounts):

No Cheating or Computer Help

You can NEVER use chess programs (Chessmaster, Fritz, etc) to analyze current ongoing games unlessspecifically permitted (such as a computer tournament, etc). The only type of computer assistance allowed is games databases for opening lines in Turn-based Chess and Vote Chess. You cannot receive ANY outside assistance on Live Chess games.

if chessmates are using "computer engines" during a chess game, what would be the difference if i had my "highly rated friend" look at the game im playing and advise me of my move?   i guess ive been under what now i see as an illusion of both parties doing their own thinking in a correspondence game. what the heck?

And neither is playing chess, it's simply doing the clerical work of entering someone (or something) else's moves for them/it.

In correspondence chess it's allowed just lame.
More so it's completely useless/counterproductive if you are <2000 Elo. What do you honestly expect to gain from using a database? Non titled players (let alone most people here including myself) following deep theoretical lines is quite laughable.
You are better off calculating and trying to understand opening play sometimes ending up in theoretical positions all by yourself. Then you can say you have understood and learned something. > improvement.

I don't think you understand how databases are ideally used.  It's not rote copying of someone else's game -- all you have to do is deviate from the line to foil that approach.  Opening databases have many, many pitfalls if not used in conjunction with a deeper understanding of the opening you're playing.

I am a bit uneasy about database use and in most games I don't find the need to use one. I get fun out of exploring for myself the openings with which I have some familiarity and am too lazy or maybe find it too disruptive to analysis to go off and consult a book or a database.

But I have occasionally used a database when an opponent plays a line on move one or two or three with which I am wholly unfamiliar. I don't want to fall foul of some egregious trap and looking at the standard responses shown in the database is a shortcut to avoid that.

I also use a database quite often in vote chess where I find it is a common resource for people to employ. In that context I have found it helpful to follow the main line, as chosen by those whose games are in that database, to the point where one or two full games are given. If the players are top class you get the chance to see how the line you are playing down pans out in the later stages of the middle game and the end game. And if the games you find are more at the level of the people taking part in the vote chess match you get the chance to see what blunders may look attractive to the collective mind or gain material helpful in explaining your views to your team mates.

The discussion here, and particularly the helpful recital of chess.cm's own rule, would seem conclusive in answering the OP; there plainly is no unwritten rule. The majority of people are happy with the written rule and are happy for their opponents to use databases if they wish.

The suggestion to propose a specific agreement with each opponent or to join/form a group which bans database use seems to me also well made. I would be entirely happy to receive a message when a game was getting under way proposing a mutual agreement not to consult a database. For myself I would fall in with an opponent's wishes and play the game but if another opponent did not wish to agree then I can't really see that aborting the game would be irksome.

That would not work for tournaments or group matches so perhaps the idea of a group which operated the unwritten rule is one the OP might pursue.

I think he's under the impression that you can "channel a master" by simply copying their openings from out of an opening database (notwithstanding the fact that it takes two to follow a specific game's line).

But if you follow the opening developments from Capablanca, I´m sure that you won´t get too far these days.

Because you are trusting the work of others over your own. That's the whole point of using a database isn't it? 
GM level explanations to go with theoretical lines hardly help you if you are faced with sudden patzerish offbeat moves that the GM didn't even deem worthy to discuss. But you haven't worked out the subtleties and tactics of the position yourself which you had if you had worked out the position and steered it into something you like.

Which one gives you a deeper understanding? What did you learn and remember better in school, the stuff your teacher told you "in theory" or the stuff you figured out on your own "in practise"?

You might not even like the type of position you've gotten yourself into even when the GM says it's "good". But you haven't got the skills to turn the "good" into a full point worse you might not even have the skills to cope with the "bad" the opponent has for you here even when it's trivial for the GM.
Sure, a database might give you immediate result in a single game but I suppose in chess the idea is to improve and in chess typically the hard work you put in > pays off. Also remember that in OTB you can't use databases.

Pearls before swine.

Not without understanding WHY and more importantly does it apply to the current position? Indeed I break/forget the rules you mentioned quite often if the position demands it and not before hard calculation and consideration to the best of MY ability. I do not just "trust" what the master has said if it does not agree with my own understanding or findings. That is what playing and getting better at chess (or most things in life) is all about.

All that resting and avoiding any in depth point made somehow carries over well.

I explained why it's silly and even counterproductive when you don't have the chess understanding and skills. You offered nothing in return.

Way up in the ranks it's a different story because those players are able to utilise the theory. (that's the whole point) Ie. recognise and pounce on some vague weakness that's created etc. (In the case of correspondence they might even create theory.) But we're not talking about those kinds of players are we? You nor anyone in this thread (well maybe, i haven't checked everyone's rating, let's just say you and me then.) comes even close to half that level. So again what do you hope to gain from using databases?

Oh no you didn't.

Thank you owltuna, I found your explanations clear and concise.  Keep up the good work.

Correspondence chess allows for database use and those unaware only have themselves to blame. It's not cheating and can be a very good study tool for learning openings and why certain moves or move sequences are preferable. There is no reasonable way to prevent database use anyway, as I've known 1200 OTB players to know a lot of opening theory or specific openings very deep. Instead of complaining about it just avoid correspondence chess, accept your opponents may use it, or use it yourself. It can Be a great learning tool.