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When I start bitcoind, I like to set a -minrelaytxfee to save bandwidth on transactions that will likely never make it in to the blockchain (because their fees are too low).

However, when the network is under low load, I would be happy to reduce the -minrelaytxfee so that my node receives more of the transactions on the network.

Is there any way I can dynamically change the minrelaytxfee whilst my node is running?

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No, there is no way to do that.

However you could make your mempool smaller and that would have a similar effect. The mempool has its own minmempoolfee. The in-practice minrelayfee is the maximum of the -minrelaytxfee and the minmempoolfee. The minmempoolfee will change when the mempool becomes full, and decreases when it has space. So if you set your -maxmempool to be much smaller, you would get a similar effect to changing -minrelaytxfee dynamically.

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  • Thanks Andrew, this is interesting to learn. Do you know of any documentation on how -maxmempool adjusts the minmempoolfee?
    – inersha
    Aug 14 '17 at 22:31
  • @inersha When transactions are evicted from the mempool due to being at the bottom of a too-large mempool when sorted by feerate, the effective minrelayfee is raised to be the feerate of the evicted transactions.
    – Pieter Wuille
    Aug 14 '17 at 23:18
  • @PieterWuille Excellent, thanks Pieter. What causes minmempoolfee to return back to a lower value (i.e. back to -minrelaytxfee)? Is it when a transaction is received that does not have to evict another one?
    – inersha
    Aug 14 '17 at 23:22
  • It continuously goes down, very slowly, halving every 3 to 12 hours, until it has to be bumped again due to an eviction.
    – Pieter Wuille
    Aug 14 '17 at 23:43

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