The scds_fm_action() function uses the probe_status of the data service in conjunction with the past history of failures to take one of the following actions:

• Restart the application.
• Fail over the resource group.
• Do nothing.

Use the value of the input probe_status argument to indicate the severity of the failure. For example, you might consider a failure to connect to an application as a complete failure, but a failure to disconnect as a partial failure. In the latter case you would have to specify a value for probe_status between 0 and SCDS_PROBE_COMPLETE_FAILURE.

The DSDL defines SCDS_PROBE_COMPLETE_FAILURE as 100. For partial probe success or failure, use a value between 0 and SCDS_PROBE_COMPLETE_FAILURE.

Successive calls to scds_fm_action() compute a failure history by summing the value of the probe_status input parameter over the time interval defined by the Retry_interval property of the resource. Any failure history older than Retry_interval is purged from memory and is not used towards making the restart or failover decision.

The scds_fm_action() function uses the following algorithm to choose the action to take:

Restart

If the accumulated history of failures reaches SCDS_PROBE_COMPLETE_FAILURE, scds_fm_action() restarts the resource by calling the STOP method of the resource followed by the START method. It ignores any PRENET_START or POSTNET_STOP methods defined for the resource type.

The status of the resource is set to SCHA_RSSTATUS_DEGRADED by making a scha_resource_setstatus() call, unless it is already set.

If the restart attempt fails because the START or STOP methods of the resource fail, a scha_control() is called with the GIVEOVER option to fail the resource group over to another node. If the scha_control() call succeeds, the resource group is failed over to another cluster node and the call to scds_fm_action() never returns.

Upon a successful restart, failure history is purged. Another restart is attempted if and only if the failure history again accumulates to SCDS_PROBE_COMPLETE_FAILURE.

Failover

If the number of restarts attempted by successive calls to scds_fm_action() reaches the Retry_count value defined on the resource, a failover is attempted by making a call to scha_control() with the GIVEOVER option.

The status of the resource is set to SCHA_RSSTATUS_FAULTED by making a scha_resource_setstatus() call, unless it is already set.

If the scha_control() call fails, the entire failure history maintained by scds_fm_action() is purged.

If the scha_control() call succeeds, the resource group is failed over to another cluster node and the call to scds_fm_action() never returns.

No action

If the accumulated history of failures remains below SCDS_PROBE_MAX_THRESOLD, no action is taken. In addition, if the probe_status value is 0, which indicates a successful health check of the service, no action is taken, irrespective of the failure history.

The status of the resource is set to SCHA_RSSTATUS_OK by making a scha_resource_setstatus() call. unless it is already set.

The following parameters are supported:

handle

The handle returned from scds_initialize(3HA).

probe_status

A number you specify between 0 and SCDS_PROBE_COMPLETE_FAILURE that indicates the health of the data service. A value of 0 implies that the recent data service health check was successful. A value of SCDS_PROBE_COMPLETE_FAILURE means complete failure and implies that the service is unhealthy. You can also supply a value in between 0 and SCDS_PROBE_COMPLETE_FAILURE that implies a partial failure of the service.

elapsed_milliseconds

The time , in milliseconds, to complete the data service health check. This value is reserved for future use.

The scha_cluster_open() function returns the following:

0

The function succeeded.

non-zero

The function failed.

SCHA_ERR_NOERR

No action was taken, or a restart was successfully attempted.

SCHA_ERR_FAIL

A failover attempt was made but it did not succeed.

SCHA_ERR_NOMEM

System is out of memory.

/usr/cluster/include/rgm/libdsdev.h

include file

/usr/cluster/lib/libdsdev.so

library

See attributes(5) for descriptions of the following attributes:

scds_initialize(3HA), scha_calls(3HA), scha_control(3HA), scha_fm_print_probes(3ha), scds_fm_sleep(3HA), scha_resource_setstatus(3HA), attributes(5)