The maximum active routing steps (MAXACT) parameter of the routing entry specifies the maximum number of routing steps (jobs) that can be active at the same time through this routing entry.
In a job, only one routing step is active at a time. When a subsystem is active and the maximum number of routing steps is reached, any subsequent attempt to start a routing step through this routing entry fails. The job that attempted to start the routing step is ended, and a message is sent by the subsystem to the job's log.
Typically there is no reason to control the number of routing steps, thus the recommended value is *NOMAX.