Generally, you would just add one entry like this one.
Opt Seq Nbr Program Library Compare Value
999 QCMD QSYS *ANY
On the SBMJOB command there is an option to put in RTGDTA. When a job enters the subsystem, it looks at that value and then tries to find it in the Routing enties in the susbsys. If found. it uses the information from the subsystem decription.
You might use this is you setup a class with a different priority or timeslice and the same Subsystem.