Setting the Interval Between Fault Monitor Probes

To determine whether SAP xserver and the SAP DB database instance are operating correctly, the Sun Cluster HA for SAP DB fault monitors probe these resources periodically. The interval between fault monitor probes affects the availability of each resource and the performance of your system as follows:

• The interval between fault monitor probes affects the length of time that is required to detect a fault and respond to the fault. Therefore, if you decrease the interval between fault monitor probes, the time that is required to detect a fault and respond to the fault is also decreased. This decrease enhances the availability of the resource.

• Each fault monitor probe consumes system resources such as processor cycles and memory. Therefore, if you decrease the interval between fault monitor probes, the performance of the system is degraded.

The optimum interval between fault monitor probes also depends on the time that is required to respond to a fault in the resource. This time depends on how the complexity of the resource affects the time that is required for operations such as restarting the resource.

For example, SAP xserver is a much simpler resource and can be restarted much quicker than SAP DB. Therefore, the optimum interval between fault monitor probes of SAP xserver is shorter than the optimum interval between probes of SAP DB.

To set the interval between fault monitor probes, set the Thorough_probe_interval system property to the interval in seconds that you require. Set this property for each resource that contains a Sun Cluster HA for SAP DB fault monitor that you need to tune. The resource types of these resources are shown in Table 1–3.