Currently the mempool isn't persisted across restarts. The historical argument against doing this is that it would make transactions immortal. Expiration now addresses that issue.

Without preserving the mempool node behavior changes drastically across restarts which complicates production use (e.g. mining overly small/low fee blocks) as well as development testing. The lack of retention also causes the loss of txn priority modifications made with prioritisetransaction which makes the API less reliable.

#endif
    fIsBareMultisigStd = GetBoolArg("-permitbaremultisig", DEFAULT_PERMIT_BAREMULTISIG);
    fAcceptDatacarrier = GetBoolArg("-datacarrier", DEFAULT_ACCEPT_DATACARRIER);
    nMaxDatacarrierBytes = GetArg("-datacarriersize", nMaxDatacarrierBytes);
    
    SetMockTime(GetArg("-mocktime", 0)); 
    ServiceFlags nLocalServices = NODE_NETWORK;
    ServiceFlags nRelevantServices = NODE_NETWORK;
    if (GetBoolArg("-peerbloomfilters", DEFAULT_PEERBLOOMFILTERS))
        nLocalServices = ServiceFlags(nLocalServices | NODE_BLOOM);
    nMaxTipAge = GetArg("-maxtipage", DEFAULT_MAX_TIP_AGE);
    fEnableReplacement = GetBoolArg("-mempoolreplacement", DEFAULT_ENABLE_REPLACEMENT);
    if ((!fEnableReplacement) && mapArgs.count("-mempoolreplacement")) {
        
        std::string strReplacementModeList = GetArg("-mempoolreplacement", "");  
        std::vector<std::string> vstrReplacementModes;
        boost::split(vstrReplacementModes, strReplacementModeList, boost::is_any_of(","));
        fEnableReplacement = (std::find(vstrReplacementModes.begin(), vstrReplacementModes.end(), "fee") != vstrReplacementModes.end());
    }
    if (!mapMultiArgs["-bip9params"].empty()) {
        
        if (!chainparams.MineBlocksOnDemand()) {
            return InitError("BIP9 parameters may only be overridden on regtest.");
        }
        const vector<string>& deployments = mapMultiArgs["-bip9params"];
        for (auto i : deployments) {
            std::vector<std::string> vDeploymentParams;
            boost::split(vDeploymentParams, i, boost::is_any_of(":"));
            if (vDeploymentParams.size() != 3) {
                return InitError("BIP9 parameters malformed, expecting deployment:start:end");