When a threshold is crossed, the SAP ASE server executes the associated stored procedure. The SAP ASE server uses the following search path for the threshold procedure:
If the procedure name does not specify a database, the SAP ASE server looks in the database in which the threshold was crossed.
If the procedure is not found in this database and the procedure name begins with “sp_”, the SAP ASE server looks in the sybsystemprocs database.
If the procedure is not found in either database, the SAP ASE server sends an error message to the error log.
The SAP ASE server uses a hysteresis value, the global variable @@thresh_hysteresis, to determine how sensitive thresholds are to variations in free space. Once a threshold executes its procedure, it is deactivated. The threshold remains inactive until the amount of free space in the segment rises to @@thresh_hysteresis pages above the threshold. This prevents thresholds from executing their procedures repeatedly in response to minor fluctuations in free space.