The current thinking is that there are 3 types of schedulers, paa supply two of these three types of scheduler.

• event-driven or real-time
• static, pre-emptive and time driven
• dynamic, pre-emptive and time driven

These are described below in more detail. In our experience, some manufacturers offer one scheduler dynamic, pre-emptive and time driven to give the flexibility of event-driven and time driven schedulers. However, paa believe that the best solution is to offer pure examples of each type of scheduler.

With a real-time scheduler, the system will run 'flat out' with little or no control of timings (although OVERLORD does allow key timing for one process). There is resource sharing but little or no resource planning, so if a resource is required the process has to wait until the resource is released. Uses include; simple processes such as plate processing through devices such as plate reader or plate.

Process Analysis & Automation have Overlord2 in the is category of schedulers. Overlord2... Another example is VWorks.

With a pre-emptive scheduler, the system runs to a planned time schedule, with total control of the time windows for each element in the system. There is resource sharing and there will never be any conflict in the use in the system resource (unless there is an error, when under certain circumstances the time windows will shift). Uses include; cell culture and processing.

The strength of this type of schedule is the guarantee of samples being treated in an identical way. There is little scone for decisions in the schedule. A pre-emptive is TIME driven.

Process Analysis & Automation have OVERLORD Scheduler in this category of schedulers. OVERLORD Scheduler ...

Runs in the same way as the static and pre-emptive category above, but allows rescheduling during the run if required, for example when an error state is detected. The ability to reschedule during the run has been added to try and give the degree of flexibility that is offered by a dynamic scheduler. Examples of this type of scheduler include SAMI, POLARA, EVOware, FACTS and Momentum.