The Resource Group Manager (RGM) is implemented as a daemon, rgmd, that runs on each member node of the cluster. All of the rgmd processes communicate with each other and act together as a single cluster-wide facility.
Whenever a node boots or crashes, the RGM attempts to maintain availability of all managed resource groups by automatically bringing them online on appropriate masters.
If a particular resource fails, its monitor program can request that the resource group be restarted on the same master or switched to a new master.
The cluster administrator can issue an administrative command to request one of the following actions:
Change mastery of a resource group
Enable or disable a particular resource within a resource group
Create, delete, or modify a resource, a resource group, or a resource type
Whenever the RGM activates configuration changes, it coordinates its actions across all member nodes of the cluster. This kind of activity is known as a reconfiguration. To effect a state change on an individual resource, the RGM invokes a resource-type specific callback method on that resource. Callback methods are described in Callback Methods.