WAITSCAN parameter

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Wait scan interval


Default value
Parameter type
Where set
On User 0's parameter line or reset by system manager
Related products
Model 204 V2.1 or earlier


The real-time interval that is allowed to pass between wait queue checks

WAITSCAN specifies the period in milliseconds at which lower priority CPU-bound users are preempted by higher priority users whose I/O has completed.

Decreasing this parameter reduces the time it takes for a lower priority user to get preempted, thus increasing the response differential between low and high priority users. However, decreasing this value also increases scheduler overhead. Because the effect on scheduler overhead is particularly strong, do not decrease the parameter without sufficient reason.

Increasing this parameter allows CPU-bound users to periodically lock out other users, reducing system throughput.