Applies To:
  • CitectSCADA 4.xx

I would like some explanation regarding the scheduler cycles that can be viewed in the <PAGE GENERAL> in the Kernel. Running ver 3.40 in Win95 can show a very high value as 25000-30000 while running the same application in ver 4.20 and Win95 can show values of about 100 times less (200-400). There is no difference in response in the application.

Can you please clarify why the results in the kernel are so different?


Under 32 bit versions the schedule cycles is much lower than 16 bit versions. This is because with 32 bit versions Citect is using Windows to perform the process scheduling. Under 16 bit the Citect kernel controls the scheduling and so the scheduler cycles is much higher. With the 16 bit version the scheduler cycles will be higher if Citect is not very busy. The busier Citect is the lower the value. It will also depend on how fast your computer is. The faster the computer the higher the scheduler cycles. Typical values of Scheduler Cycles in 16 bit would be between 10,000 to 50,000 (may be as low as several hundred on heavily loaded systems). With the 32 bit version the scheduler cycles will depend on how busy Citect is. The busier Citect is the higher the value. Typical values of the Scheduler Cycles in Citect in 32 bit would be between 100 and 1000.