Sun Cluster 3.1 Data Services Developer's Guide

The Update Method

The RGM calls the Update method of a resource type implementation to apply any changes that were made by the system administrator to the configuration of the active resource. The Update method is only called on nodes (if any) where the resource is currently online.

The changes that have just been made to the resource configuration are guaranteed to be acceptable to the resource type implementation because the RGM runs the Validate method of the resource type before it runs the Update method. The Validate method is called before the resource or resource group properties are changed and the Validate method can veto the proposed changes. The Update method is called after the changes have been applied to give the active (online) resource the opportunity to take notice of the new settings.

A resource type developer needs to cautiously decide which properties are to be dynamically updatable and mark those with the TUNABLE=ANYTIME setting in the RTR file. Typically any property used by the fault monitor daemon of a resource type implementation could be made dynamically updatable provided the Update method implementation at least restarts the monitor daemon.

Possible candidates are

These properties affect the way a fault monitor daemon does health checking of the service, how often it does it, what history interval it uses to keep track of the errors, and what are the restart thresholds set on it by PMF. To implement updates of these properties the utility scds_pmf_restart() is provided in the DSDL.

If a resource type developer identifies the need to make a resource property dynamically updatable where modification of that property might have an effect on the running application, the resource type developer needs to implement the appropriate actions so that the updates to that property are correctly applied to any running instances of the application. Currently there is no way to facilitate this via the DSDL. Update is not passed the modified properties on the command line (as is Validate).