That's not how it works on z/OS (OS/MVS), DOS/VSE & OpenVMS.
On them, you have "named batch queues". Each queue has a default
(in Unix terminology) niceness level, and "width" (like how a
bank branch has a single line feeding multiple teller windows,
the "width" defines the number of jobs that can be in the Running
state, whereas the jobs standing in "line" are Pending). Also,
there is a job priority, so that important Pending jobs jump to
the front of the line, and less important jobs fall to the rear.
Just like with "at", jobs can be scheduled to run at various
times. Of course, if the execute slots are all full at a job's
run time, it goes not to Executing but to Holding state.