Using scheduler rules

The Scheduler uses these types of rules to allocate resources for working on an operation:

Order Release Rule (ALTSCHED.ORDRELRL): Controls how the Scheduler processes orders when two or more orders are released at the same date and time. By default, orders with the lowest priority number are processed first.
Sequencing Rule (RESRC.SEQRL): Sequences the waiting requests in a resource’s request queue. For example, "loads for operations with the earliest due dates are listed first." By default, the rule is First In First Out (FIFO).
Selection Rule (RESRC.SELRL): Controls how the resource selects the next waiting request from the queue. For example, "select the load with the least setup time based on the first downstream operation." By default, no selection rule is defined and requests are selected in the sequence they appear in the request queue.
Resource Group Member Selection Rule (RGRP.ALLOCRL): Controls how the Scheduler selects a resource from a resource group to allocate to a load. For example, "select the resource that has been idle the longest." By default, the resource listed first in the resource group record is selected first.

Note: When a load arrives at an operation, the Scheduler requests all required resources in the required resource group, forcing each to check its request queue only after all loads scheduled at the same time have arrived. This prevents a lower-priority load from allocating a resource because it arrives when the resource is available, even though a load with higher priority is scheduled to arrive at the same time.

The Scheduler rule types are described in more detail in the next sections.