Controlling How Often sp_thresholdaction Executes

SAP ASE uses a hysteresis value, the global variable @@thresh_hysteresis, to control the sensitivety levels of thresholds to variations in free space.

A threshold is deactivated after it executes its procedure, and remains inactive until the amount of free space in the segment rises @@thresh_hysteresis pages above the threshold. This prevents thresholds from executing their procedures repeatedly in response to minor fluctuations in free space.

You cannot change the value of @@thresh_hysteresis.

For example, when the threshold in the previous figure executes sp_thresholdaction, it is deactivated.

In the following figure, the threshold is reactivated when the amount of free space increases by the value of @@thresh_hysteresis:

Graphic showing the layout of the log segment and the placement of the last-chance the middle of the free space and the placement of @@thresh_hysteresis.