What is your IS version? and the class/method used in your code snippet can be obsolete on the new verison of IS.
System thread can be found on IS page by going to the link “http://localhost:5555/WmRoot/server-threads-new.dsp”, ie., Server > Statistics > System Threads there will be a underlying service “wm.server.query:getThreadList” in WmRoot which can get you the details. Note, that services (internal) used from WmRoot is at your own risk as this may change from version to version and there is no documentation on the change.
To make WmRoot visible on your Designer IDE, add the below setting and refersh your Designer session.
watt.server.ns.hideWmRoot=false
To configure the Server Thread Pool go to “Settings > Resources”
#Integration-Server-and-ESB#webMethods