To disable logging of incoming messages completely, the OnixS::FIX::Session::logInboundMessages option should be used. OnixS::FIX::Session::inboundMessageLogFilter exposes the ability to filter out incoming messages of the specified types from the log file.

        Session::InboundMessageLogFilter filter;
        filter.insert("W");
        filter.insert("X");
        session.inboundMessageLogFilter(filter);

To disable logging of outgoing messages completely, the OnixS::FIX::Session::logOutboundMessages option should be used. OnixS::FIX::Session::outboundMessageLogFilter exposes the ability to filter out outgoing messages of the specified types from the log file.

        Session::OutboundMessageLogFilter filter;
        filter.insert("W");
        filter.insert("X");
        session.outboundMessageLogFilter(filter);

By default, the FIX Engine uses the UTC time in log files, but if you need to use the local time then you can set the OnixS::FIX::EngineSettings.localTimeUsage option to true.