Hysteresis value

To keep threshold procedures from firing continuously in response to minor fluctuations in space usage, Adaptive Server uses the Tolerance (Hysteresis) value. This server-wide value, stored in the system variable @@thresh_hysteresis, is specified in data pages. Before a threshold that has been activated and has triggered a stored procedure can be activated again, the space usage on the segment must decrease by at least the hysteresis value. Similarly, any two thresholds on a segment must be at least two hysteresis values apart.

For example, if one threshold is set at .2MB and the hysteresis value for the Adaptive Server is 64 pages (.128MB), the closest you could place the next threshold would be .2+ (2*.128), or .456MB.