Thanks Eduard,

I think I finally found the answer, use the correct class.  Using %SYS.Journal.System instead of Config.Journal updating and reading the setting is very easy.

 returnValue = dbnative.classMethodValue("%SYS.Journal.System","SetPrimaryDirectory","/iris/journal/")

 print("Set Primary Directory: ", returnValue )

  returnValue = dbnative.classMethodValue("%SYS.Journal.System","GetPrimaryDirectory")

  print("Get Primary Directory: ", returnValue )

Thanks for your reply.