Normal big-enough transaction with 0 fee is not confirmed for hours

[oleganza]

Interesting. I have a transaction that sends around 0.1 BTC from a single 0.4 BTC output that was confirmed >100 blocks before. It is not included in any block for 7 hours already. I've been sending similar transactions with zero fees before from the same blockchain.info iPhone app and it was always confirmed quickly enough. What could be the reason for the problem? Is it just the mining fee that is suddenly required, or we are hitting block size limit, or one of the addresses could be banned? (Destination addresses are a new one, not SatoshiDice, and the same my address for the change.)

[SomeWhere]

It took 10 hours for a 1.5 BTC transaction of mine to be confirmed once without fees. It's variance. It can take a really long time depending on luck pretty much.

[deepceleron]

A transaction sending 0.4 BTC with 100 confirmations is not high enough priority to send with no fee.

priority = sum(input_value_in_base_units * input_age)/size_in_bytes

((0.4 * 100,000,000) * 100) / 258 = 15,503,875

Transactions need to have a priority above 57,600,000 to avoid the enforced limit. I would recommend ANY payment include a fee even if it would qualify to be free, as "free transaction" space in blocks is limited, and profit-motivated miners have no incentive to include free transactions over those with fees.

[oleganza]

A transaction sending 0.4 BTC with 100 confirmations is not high enough priority to send with no fee.

priority = sum(input_value_in_base_units * input_age)/size_in_bytes

((0.4 * 100,000,000) * 100) / 258 = 15,503,875

Transactions need to have a priority above 57,600,000 to avoid the enforced limit. I would recommend ANY payment include a fee even if it would qualify to be free, as "free transaction" space in blocks is limited, and profit-motivated miners have no incentive to include free transactions over those with fees.

Thanks for the details. I'll check the source code.