Specifying the Response to a Fault

The SAP DB fault monitor responds to the following faults in SAP DB:

• A status of the SAP DB database instance that is not ONLINE, for example, OFFLINE or ADMIN

• Unexpected termination of the parent kernel process of the SAP DB database instance

The SAP DB fault monitor also responds to the unavailability of SAP xserver. This fault monitoring supplements the fault monitoring that the SAP xserver fault monitor provides.

The SAP xserver fault monitor responds to following faults:

• Unavailability of SAP xserver

• Persistent system errors

The Sun Cluster HA for SAP DB fault monitors enable you to specify the response to these faults. Specifying the response to a fault involves the following tasks:

• Defining the criteria for persistent faults

• Disabling the failover of the SAP DB resource

• Forcing the SAP DB database instance to be restarted if the parent kernel process is terminated

Defining the Criteria for Persistent Faults

To minimize the disruption that transient faults in a resource cause, a fault monitor restarts the resource in response to such faults. For persistent faults, more disruptive action than restarting the resource is required:

• For the SAP DB resource, the fault monitor fails over the resource to another node. The SAP DB resource is a failover resource.

• For the SAP xserver resource, the fault monitor takes the resource offline. The SAP xserver is a scalable resource.

The fault monitors treat a fault as persistent if the number of attempts to restart a resource exceeds a specified threshold within a specified retry interval. Defining the criteria for persistent faults enables you to set the threshold and the retry interval to accommodate the performance characteristics of your cluster and your availability requirements.

Dependencies of the Threshold and the Retry Interval on Other Properties

The maximum length of time that is required for a single restart of a faulty resource is the sum of the values of the following properties:

• Thorough_probe_interval system property

• Probe_timeout extension property

To ensure that you allow enough time for the threshold to be reached within the retry interval, use the following expression to calculate values for the retry interval and the threshold:

retry-interval ≥ threshold × (thorough-probe-interval + probe-timeout)

System Properties for Setting the Threshold and the Retry Interval

To set the threshold and the retry interval, set the following system properties:

• To set the threshold, set the Retry_count system property to the maximum allowed number of restarts.

• To set the retry interval, set the Retry_interval system property to the interval in seconds that you require.

Set these properties 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.

Other Effects of the Retry Interval

Besides defining a criterion for persistent faults, the retry interval affects the response of a fault monitor to the following faults:

• Unavailability of SAP xserver that the SAP DB fault monitor detects. If the SAP DB fault monitor detects that SAP xserver is unavailable twice within the retry interval, the SAP DB fault monitor restarts SAP xserver.

• Persistent system errors. A persistent system error is a system error that occurs four times within the retry interval. If a persistent system error occurs, the fault monitor restarts SAP xserver.

Disabling the Failover of the SAP DB Resource

By default, failover of the SAP DB resource is enabled. The fault monitor fails over the SAP DB resource in response to a persistent fault. A persistent fault occurs if the number of attempts to restart exceeds Retry_count within the time that Retry_interval specifies.

Disable the failover of the SAP DB resource if you require the fault monitor to restart the SAP DB even in response to a persistent fault. When failover is disabled, the fault monitor reports a persistent fault in a resource by setting the status of the resource to faulted.

To disable the failover of the SAP DB resource, set the Failover_enabled extension property of the SUNW.sapdb resource to False.

Forcing the SAP DB Database Instance to Be Restarted if the Parent Kernel Process Is Terminated

By default, unexpected termination of the parent kernel process does not cause the SAP DB fault monitor to restart the SAP DB database instance. The SAP DB database instance can continue to function without the parent kernel process. Restarting the SAP DB database instance in this situation might cause unnecessary unavailability of the SAP DB database instance. Therefore, you should force the SAP DB database instance to be restarted only if you require a feature that the parent kernel process provides. An example of such a feature is maintaining the integrity of the log history.

To force the SAP DB database instance to be restarted if the parent kernel process is terminated, set the Restart_if_Parent_Terminated extension property of the SUNW.sapdb resource to True.