Occasionally, operations scheduled in the MIS are not recorded in the Scheduler. This fact might not be detected by the user of the Scheduler and, consequently, these operations may be scheduled again although they were already scheduled in the MIS.
The reason for this is that layouts or sequence templates that are part of the process networks of the jobs scheduled in the MIS could be deleted by the prepress user after scheduling. This occurs when there are a great number of changes in the job settings between setup of a job in the MIS and the concluding job configuration for production.
Such jobs then do not display in the Scheduler because the process networks are the basis for scheduling.
To avoid such situations, you can do scheduling with "placeholder" jobs instead of real jobs.
Prerequisite: The "Preliminary scheduling with placeholder jobs" option must be enabled in the "Presettings" dialog (see "Preliminary scheduling with placeholder jobs").