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Using nice and priocntl to Change UNIX Execution Priority
Oracle Tips by Burleson Consulting

Using nice and priocntl to Change UNIX Execution Priority

While CPU shortages generally require the addition of more processors on the server, there are some short-term things that you can do to keep running until the new processors arrive. Within the server, all tasks are queued to the CPUs according to their dispatching priority. The dispatching priority is commonly referred to as the nice value for the task. Those tasks with a low nice value are scheduled ahead of other tasks in the CPU queue, while those tasks with a high nice value are serviced later.

In emergency situations where you cannot immediately get more CPUs, you can assign a very low dispatching priority to the Oracle background process, causing them to get CPU cycles ahead of other tasks on the server. This will ensure that Oracle gets all of the CPU that it requires, but it will slow down any external tasks that are accessing the Oracle database. To do this, the systems administrator can alter the CPU dispatching priority of tasks with the UNIX nice or priocntl commands. The UNIX nice command is used to change dispatching priorities, but these numeric ranges vary by operating system. In general, the lower the nice value, the higher the priority.