I think the WRKACTJOB option can not be always used. We have many interactive subsystems and QINTER is not used. I will choose the go assist option and the WRKUSRJOB (the result is the same), they are usefull.

Another command is been there to search of the interactive user being logged in to the server.. by using the command WRKUSRJOB, in that status been *ACTIVE, job type is *INTERACT..
if u want to kill the job, use option 4 to kill it..

User WRKACTJOB. User sessions will be in the QINTER subsystem. The job name is the workstation ID and the current user is the user logged in. To end the job, place a 4 next to it, and in the command line, type: OPTION(*IMMED).

That will kick the user off after the end job command is processed.

Go to As400 ASSIST menu. You can go to this menu by pressing ESC key in your keyboard while you are in a AS400 Session or by keying the command GO MENU(ASSIST).Take option;
10. Manage your system, users, and devices
Take option;
12. Work with signed-on users

All the active users will be listed for you with their display station Id’s. You could sign off (kill) any user or send messages from this screeen. The F11 key gives you some more views of this screen.