Unconfirmed transaction


2 days ago i sent 2 ZEC to other wallet with 0.001 transaction fee. I use zcash4win. However the transaction is still unconfirmed and not even included into the block. Transaction is visible on blockexplorer and zchain. Here is a link https://zcash.blockexplorer.com/tx/38e22d38959bd031e5608fc1e451fb2f39c745dfaa62c4e53152b6e8f7881277

The question is what do i do now? Is there a way to accelerate this transaction? Will it be completed someday or it will be pending forever?

Thanks for reply!

There are a number of similar posts e.g. see this one Unconfirmed transaction after 4 days; getting worried which may help you out.

The issue is that there are 197 inputs for this transaction and some of the miners limit the number of inputs they will accept (via -mempooltxinputlimit). Most notably Flypool, that controls the majority of the hashrate, which in that other thread appears to limit to 150 inputs. Some of the other miners don’t have this limit so it’s possible it will be mined when one of these other miners finds a block but you might have to be patient.

See here New Release: 1.1.0 - Electric Coin Company and the -MEMPOOLTXINPUTLIMIT DEPRECATION section, this problem has been addressed but it isn’t going to solve your immediate issue as Overwinter doesn’t activate until late June.

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hi, thank-you for your response. so worst case this transaction will be confirmed in June after the overwinter network upgrade? It’s been 12 days already. I am glad this issue is resolved going forward, I have read about the root cause of the issue.

It would have been ideal if there had been some mechanism to cancel a transaction (as long as no confirmations had started). If you think about it practically, if I actually needed this value for anything, like to use as an actual currency, it’s risky to have it stuck in limbo for some indeterminate amount of time, without any recourse to recover my coins. It is after all about $1000 USD worth in stored value.

It’ll likely be dropped from the mempool before then so likely you will have to rebroadcast it (if after Overwinter you won’t have to worry about inputs). I’m not entirely sure but the default may be 2 weeks to be dropped by the mempool? If you then did want to resend, there is a way to consolidate a large number of UTXOs (it’s an experimental feature) with z_mergetoaddress see New Release: 1.0.15 - Electric Coin Company and the UTXO AND NOTE MERGING section.

Agreed, and fortunately again with Overwinter this is addressed - see this ZIP zips/zip-0203.rst at main · zcash/zips · GitHub.

Transactions will have a new field, nExpiryHeight, which will set the block height after which transactions will be removed from the mempool if they have not been mined.

I think the default is 20 blocks so if not confirmed it is no longer stuck in limbo but removed from mempool and may be rebroadcast.

Just to update that the transaction for the original post has actually been mined now.

oh, my bad, I didn’t realize that you were actually replying to a different thread than my original… I just responded to a notification in my email. Yes, looks like zloezlo’s transaction got mined. Mine is still unconfirmed.

Thanks for the further information, that’s more than I’ve received from anyone else yet and exactly what I was looking for - how long it would take for my transaction to be either mined or dropped. Monday at 6PM CST will make 14 days (2 weeks), so i hope you are correct and it dumps my transaction Monday. I have been told that if I manually upgrade the mining fee that it mitigates this problem . If I send again, i will split this transaction into 2 and increase the mining reward.

It isn’t necessary to increase the fee as there isn’t fee pressure on Zcash at the moment. This was a huge deal with Bitcoin as miners prioritize based on fees but the default fee is fine right now - it’s just that (some) miners never included the transaction into their mempool due to that setting above.

After a little more research I think I am wrong about the default mempool expiry time see Node-configured wall-clock mempool transaction expiry · Issue #2384 · zcash/zcash · GitHub and this is resolved (with Overwinter) by the Transaction Expiry linked to above.

I’m guessing some of the other proposed solutions are variants of clearing it from your own mempool then rebroadcasting the transaction in the hope it is picked up by one of the miners who have no record of it (so don’t see it as an invalid transaction).