bitcoin-bitcoin-core/doc/release-notes-27460.md

• A new importmempool RPC has been added. It loads a valid mempool.dat file and attempts to add its contents to the mempool. This can be useful to import mempool data from another node without having to modify the datadir contents and without having to restart the node. (#27460)
  • Warning: Importing untrusted files is dangerous, especially if metadata from the file is taken over.
  • If you want to apply fee deltas, it is recommended to use the getprioritisedtransactions and prioritisetransaction RPCs instead of the apply_fee_delta_priority option to avoid double-prioritising any already-prioritised transactions in the mempool.