JobScheduler is creating and starting for a scheduled job or jobchain-node a separate process. The number number of parallel processes can be limited. The workload of the job has no impact on JobScheduler. Sometimes the size of the logging-file could have create a problem due to some restrictions on the used database.
If the program which has to be scheduled by JS can be started in a shell (windows or unix) the job-type must be a shell-job. All programs, which are started by cron or taskplaner should be running in the shell-job of JobScheduler as well.
It is important to keep in mind, that JobScheduler is running as a service (windows) or as a demon (unix). JobScheduler must have at least all the requiered permissions for accessing the resources, which are needed to execute the program.