1). Follow the instructions in section the Spotfire Server documentation to export the default service configuration. Example for version 7.6: https://docs.tibco.com/pub/spotfire_server/7.6.0/doc/html/TIB_sfire_server_tsas_admin_help/GUID-D6B0AF26-4931-4FDE-9E7F-A487376402C7.html.

2). Edit the Spotfire.Dxp.Worker.Host.exe.config file. Below the tag </applicationSettings> add the following (if not already present):

  <system.diagnostics>
    <trace autoflush="true">
      <listeners>
        <add
            name="textWriterTraceListener"
            type="System.Diagnostics.TextWriterTraceListener"
            initializeData="C:\temp\logs\log4net.txt" />  <!-- Use a path that exists -->
      </listeners>
    </trace>
  </system.diagnostics>

  <appSettings>
    <!-- Do not edit these settings if you are not really sure what you are doing!
         To enable log4net debug logging, set Quiet=false and Debug=true -->
    <add key="log4net.Internal.Quiet" value="false" />
    <add key="log4net.Internal.Debug" value="true" />
  </appSettings>

Make sure to set the initializeData path to where you want the log4net debug log be written to.

3). Import the updated config to a new name (by following follow the instructions in section the Spotfire Server documentation).

4). Go to Nodes & Services and edit all services to use the new configuration. This should automatically restart the service instances.