The RGM runs the Monitor_check callback method on a resource on a node for the specified resource to ascertain whether the cluster node is capable of mastering the resource. In other words, the RGM runs this method to determine whether the application that is being managed by the resource can run successfully on the node.
Typically, this situation involves ensuring that all the system resources that are required by the application are indeed available on the cluster node. As discussed in Validate Method, the function svc_validate() that you implement is intended to ascertain at least that.
Depending on the specific application that is being managed by the resource type implementation, the Monitor_check method can be written to carry out additional tasks. The Monitor_check method must be implemented so that it does not conflict with other methods that are running concurrently. If you are using the DSDL, the Monitor_check method should call the svc_validate() function, which implements application-specific validation of resource properties.