Priorities range from 1 (most urgent) to 12 (least urgent). The toplevel goal of an execution always runs at the lowest priority (12).
Warning: Although it is possible to write programs that only work correctly under a particular priority ordering, such practice is strongly discouraged. Priorities should only affect efficiency, never correctness.
    [eclipse 1]: get_priority(P).
    P = 12
    yes.
    [eclipse 2]: [user].
     p :- get_priority(P), writeln(prio=P).
    user       compiled traceable 120 bytes in 0.00 seconds
    yes.
    [eclipse 3]: suspend(p, 5, X->inst), X=1.
    prio = 5
    X = 1
    yes.