Please explain how TX ID results in "No such transaction" on blockexplorer.com?

[ehiv]

Hello.  My apologies if this has been discussed, but my searching has not yet produced a satisfactory answer.

I used BitInstant today - I know, a great choice of days - to buy on MtGox.  Deposited funds, successful buy.  Done and done.  Transfer purchased BTC to my wallet, using "Green Address" option (which I have used before with no substantial delays).  This was at ~13:00 EDT.

Still showing 0/unconfirmed in the Bitcoin-Qt client.

What I don't understand is this: How can I have a transaction ID, as produced by viewing the transaction details in Bitcoin-Qt, but when entered into blockchain.info or blockexplorer.com they both state that it is an unknown transaction ID?  How can my client have received a transaction announcement (I think this is the correct term?), with an ID, and nobody else seems to know about it?

The ID is: bd4dbb5ba45770b34c60210cb58afa9fca2d186dd7aac62c02e0886e8d71a2a3
Amount: 1.1395216
Time: 4/3/13 12:54 EDT

Thanks!

[tysat]

Blockexplorer only shows confirmed transactions, as it scans the blockchain to get it's information.

[ehiv]

Wow, fast response!

Ok, maybe I didn't ask what I meant...I guess what I wanted to know is where does the generated transaction id come from?  In this case, presumably MtGox's wallet/client?

It is my understanding, then, that it is not yet appearing because their "Green Address" option is without transaction fees?  At this point the transaction is in limbo until a miner decides to include it?

Thanks!

[tysat]

I'm guessing it was delayed due to the issues MtGox has had today (DDoS I think?)...

https://blockchain.info/tx/bd4dbb5ba45770b34c60210cb58afa9fca2d186dd7aac62c02e0886e8d71a2a3

The transaction is showing up now on blockchain.info, it didn't earlier when I first posted.  I've got no idea how the green addresses actually work, so who knows when it'll actually be confirmed.

[vit1988]

I'm also waiting for a confirmation for a long time... btw. what happens if no one confirms that transaction ever?

https://blockchain.info/tx/faf86d7c6655392140c926b85d2bdeec15f123115eb3b2cde1296be4d7ca07f2

[tysat]

I'm also waiting for a confirmation for a long time... btw. what happens if no one confirms that transaction ever?

https://blockchain.info/tx/faf86d7c6655392140c926b85d2bdeec15f123115eb3b2cde1296be4d7ca07f2

0 fee, it's going to take some time

[zeroday]

Once I waited for mtgox transaction for over a week and It never came into my address.
I wrote to their support and they told me it was a glitch and re-sent coins with another transaction.

[ehiv]

I was wondering if the "issues" were responsible, too.  Also, as with other search results on related topics, I figured that as soon as I posted about it things would start to appear...

As a participant in the Bitcoin economy for several months now, and as someone who has a technical background, I thought I had a good handle on the workings of Bitcoin.  This wasn't money I couldn't afford to lose, but it was sure disconcerting to be so confused.

Like most here I really want Bitcoin to succeed, but this situation of "maybe it will be confirmed, in an hour, three hours, today, tomorrow, next week, month, etc.," sure seems to be quite a high hurdle for the less technically-inclined individuals to understand and accept.  I'm starting to find this to be a big argument against the "Bitcoin is digital cash" analogy - cash never disappears indefinitely in the middle of a transaction.  "Where is my money?" is not comforting feeling to most, especially those who still think their internet comes from AOL 

I guess I'll chalk this up to a learning experience to be used in future Bitcoin-centric discussions.  For others' benefit, I'll post back when the transaction hits 6 confirms.

Thanks again, tysat!

zeroday - I've been discovering others' experiences and the requirement to contact support.  I'm just going to wait for now.  I'm at least a bit settled to see it appear on blockchain.info under my address.  I'm not too worried.  I've lost much more money in Vegas.

[FarmerGreene]

Blockexplorer only shows confirmed transactions, as it scans the blockchain to get it's information.

BlockChain.info will show you unconfirmed transactions.  I'll explain.

Bitcoin transactions are transmitted on a peer-to-peer network.  When you transfer bitcoins, that transaction is sent from one host to the next to the next.  At this point, the "unconfirmed" transaction exists on the network.

When the Bitcoin miners start to build a block, they gather up all of these unconfirmed transactions from the network, verify them, and combine them together in a block.  Then it "mines" the block.  (Mining is the time consuming part.)  Every 10 minutes or so, a miner gets lucky and finds the lucky number to mine their block of transactions.  It transmits this completed block back out to the peer-to-peer network.  At that point, the transaction has 1 confirmation.  That block signature is included in the next block of transactions 10-20 minutes later, and that adds another confirmation.

If the Blockchain information site you use shows unconfirmed transactions, then they are showing you transactions that have been transmitted across the p2p network, but not included in a block yet.

So here's the rub.  A block can only be so big and miners want to make money.  When a miner is picking what transactions to include in a block, they prefer the ones that pay the most.  There are a lot of * transactions that need to be processed, and if you want to be at the head of the line then you should include a transaction fee.


Where do "I can't see my unconfirmed transaction" delays come from?
 - If the sender is bunching transactions to save on TX fees.
 - If the sender uses an air-gap system for security, slowing the speed that transactions reach the p2p network.
 - If the sender hasn't sent them yet.
 - p2p network propagation delay (this is fast, less than 5 minutes if you are well connected.)

Where do "My transaction isn't confirmed" delays come from?
 - Miners preferring to process transactions with a higher (non-zero) TX fee.
 - Miners ignoring Double-spend transactions.

Big takeaway: Include a transaction fee on your transactions, then the miners will prefer your transactions and confirm them faster.

* - * cough* satoshi dice *cough*

[ehiv]

This is a very clear explanation that I've been needing.  I don't think I had quite understood where the transactions "lived" until the miners chose to include them in a block.

[FarmerGreene]

Glad to help.  I'm working on a presentation like this to explain Bitcoin and the payment process to generally non-technical folks.  Any feedback?

[ehiv]

I will certainly put some thought into it and get back to you...tomorrow.  I'm calling it a day for now

I only came back tonight as I said to state that I just checked and now have 10 confirmations.

And, we learned something today.

[ehiv]

Glad to help.  I'm working on a presentation like this to explain Bitcoin and the payment process to generally non-technical folks.  Any feedback?

Thanks again for the explanation.  After mulling things over today I think it was your simple explanation of the p2p network that cleared things up for me.  I now want to learn a bit more of the technical details of p2p networks, but that's for another day.  As you essentially confirmed, my understandings of mining and transaction fees wasn't too far off, it was just the part about "where" the unconfirmed transactions existed.

As far as feedback.  I've tried to draw on my experiences with the non-technical peoples in my family and can envision a couple of questions.  I hope they can provoke some thought for your presentation.

1.  "So these miners can pick to not include my transaction if they don't want to?"
  --> Your answer for me was perfectly clear as I was already aware of transaction fees.  But, I can forsee some asking about how the fee is set, who sets it, etc.  This might be a good place to add that the "network" agrees upon the rate.  Right now it's X Btc, next month it could be agreed to be Y Btc.  If enough of the participants "decide" upon a change, then eventually the miners will move in step.  (This could also go the other way).  Also, even though you can set a default rate, sometimes you might be asked to vary it, as I've noticed a few times.  Finally, because I can also hear some balking at the idea of including a processing fee, which can initially seem counter-intuitive to the idea of a decentralized currency.  But, even at the current default rate of 0.0005 Btc, that fee is only ~$0.07 (using $135 exchange).  Compare that to Visa/MC/Amex fees or Paypal.

2.  "Why can a block only be so big?"  "Who/what determines the size?"

3. In-line with the reason for my post yesterday, "What happens if I forget to include a transaction fee?"  --> Your post from yesterday generally covers this, but I'm thinking more along the lines of "Will my transaction ever go through?  How long will I have to wait?" Etc., etc.

4.  "Can I add a fee after the transaction has been sent?" --> No.  But I'm sure you know this.

You don't have to answer these here   I'm just trying to step back to when I first started learning about bitcoin and drawing from my explanations/conversations with others.

I'd like to see your presentation when it is done!

[FarmerGreene]

Thanks for the feedback.  I'll go ahead and answer this one.

2.  "Why can a block only be so big?"  "Who/what determines the size?"
Right now, blocks are limited by the database format in the old version of BitcoinD.  The network tried using larger blocks for a while, but it caused the old BitcoinD and new BitcoinD clients to be unable to communicate.  This was a bad day.  This is the cause of the "All users of Bitcoin-Qt/bitcoind versions 0.7.2 and earlier are required to upgrade to 0.8.1 or apply a manual workaround by May 15." message at the top of every page on bitcointalk.org.

Cheers,
E2