How to do FireDAC monitoring or logging to file.   Here is a rough outline of what you need to do. The code is not ready to use as is and serves only to give you the general gist.   Add   FireDAC.Moni.Base, FireDAC.Moni.RemoteClient, FireDAC.Moni.FlatFile to your uses clause   Somewhere appropriate, create the following - I keep them in my DatabasePool class.     FTracing: Boolean  // init to False     FMonitorBy: TFDMonitorBy;  // init to mbRemote
    FMonitorLink: TFDMoniClientLinkBase; // init to nil   // Here is where the actual establishing of the tracing happens depending on the trace model. procedure TDBPool.SetMonitorBy(const Value: TFDMonitorBy); begin Lock; try if (FMonitorBy <> Value) and Assigned(MonitorLink) then FreeAndNil(FMonitorLink); FMonitorBy := Value; // mbNone or mbCustom disables the monitoring if MonitorBy = mbRemote then begin MonitorLink := TFDMoniRemoteClientLink.Create(nil); end else if MonitorBy = mbFlatFile then begin MonitorLink := TFDMoniFlatFileClientLink.Create(nil); TFDMoniFlatFileClientLink(MonitorLink).FileName := ParamStr(0)+'.'+FormatDateTime('yyyymmdd-hhnnss', Now)+'.FireDAC.log'; TFDMoniFlatFileClientLink(MonitorLink).FileAppend := False; end; if Assigned(MonitorLink) then MonitorLink.Tracing := Self.Tracing; finally Unlock; end; end; // Use Tracing to enable / disable the tracing function TDBPool.GetTracing: Boolean; begin Result := FTracing; end; procedure TDBPool.SetTracing(const Value: Boolean); begin FTracing := Value; if not Assigned(MonitorLink) then SetMonitorBy(FMonitorBy) else MonitorLink.Tracing := Self.Tracing; end; procedure TDBPool.SetMonitorLink( const Value: TFDMoniClientLinkBase); begin FMonitorLink := Value; end; // When the DB connection is created - it should assign the MonitorBy value procedure TDB_FD.CreateFireDACConnections; const OSAuthent = 'No'; begin if not Assigned(FConnection) then begin OnConnectionCreate; FConnection := TFDConnection.Create(nil); FConnection.DriverName := DBPool.DataBaseDriverName; // that you have selected - This example assumes an MSSQL driver - see other code block below FConnection.Params.Values[MSSQLParam.Server] := Trim(FHost); FConnection.Params.Values[MSSQLParam.Database] := Trim(FDatabaseName); FConnection.Params.Values[MSSQLParam.OSAuthent] := OSAuthent; FConnection.Params.Values[MSSQLParam.User_Name] := Trim(FUserName); FConnection.Params.Values[MSSQLParam.Password] := Trim(FPassword); FConnection.Params.MonitorBy := DBPool.MonitorBy; ... end;   BTW - Selecting the right DatabaseDriverName can have a significant impact on performance. Here is how I currently pick my preferred MSSQL driver.
  Why are those constants are not in the interface section of FireDAC.Phys.MSSQL, @Dmitry Arefiev?   class function TDBPoolMSSQL.FindBestDriver(const Link: TFDPhysMSSQLDriverLink): String; const // Constants copied from implementation section of FireDAC.Phys.MSSQL C_2018_ODBC = 'ODBC DRIVER 18 FOR SQL SERVER'; C_2017_ODBC = 'ODBC DRIVER 17 FOR SQL SERVER'; C_2016_ODBC = 'ODBC DRIVER 13 FOR SQL SERVER'; C_2012_ODBC = 'ODBC DRIVER 11 FOR SQL SERVER'; {$IFDEF POSIX} C_FreeTDS = 'FreeTDS'; {$ENDIF} {$IFDEF MSWINDOWS} C_2012_NC = 'SQL SERVER NATIVE CLIENT 11.0'; {$ENDIF} var DriverList : TStringList; WantedList : TArray<String>; begin Result := ''; // Blank = Default WantedList := {$IFDEF MSWINDOWS} {$IFDEF SQLNative} // defined if supposed to prioritize the old SQLNCLI11 [C_2012_NC, C_2017_ODBC, C_2016_ODBC, C_2012_ODBC] {$ELSE} [C_2018_ODBC, C_2017_ODBC, C_2016_ODBC, C_2012_NC, C_2012_ODBC] {$ENDIF} {$ENDIF} {$IFDEF POSIX} [C_2018_ODBC, C_2017_ODBC, C_2016_ODBC, C_2012_ODBC, C_FreeTDS] {$ENDIF}; DriverList := TStringList.Create; try Link.GetDrivers(DriverList); for var Wanted in WantedList do for var Driver in DriverList do begin // DebugOut('ODBC: "' + Driver + '"'); if CompareText(Wanted , Driver) = 0 then Exit(Wanted); end; finally DriverList.Free; end; end;