I have a 1500 CPU and I need to log values to a database, located on a small server connected to the PLC network. The server is running a InfluxDB for trending.

Can the PLC write directly to databases? If I can what types of databases (SQL?)?

Or is it easier to use a OPC server on the loggingserver to do this? I want to log values every 200 ms.

No, it can't write databases directly out of the box. Can it be programmed to do that ? Yes.

But much easier is to use e.g. an OPC for communication and some of the shelf software which makes a "bridge" between an OPC server and a database.

Hello gesteen

you also can use the OPC Server on the S71500 PLC if the PLC has a Firmware Version V2.X.

Here is a little example:

https://support.industry.siemens.com/cs/de/en/view/109737901

Or you can use another Software for example Industrial Databridge:

http://w3.siemens.com/mcms/automation-software/en/scada-software/scada-options/wincc-industrial-data-bridge/Pages/Default.aspx

I hope it helps.

Bye Murof

200ms is challenging.

Maybe you can contact http://www.factry.io. They have tons of experience with industrial use of InfluxDB. I had some test loggings running at 500ms.