Most RGM resource types separate their stopping and starting actions using the Stop or Postnet_stop and Start or Prenet_start methods. In some cases, such as in Oracle VM Server for SPARC that supports live migration, an entire switchover of the resource is performed by the Stop method. For example, if an Oracle VM Server for SPARC guest domain starts out on node1 and you execute a switchover to node2, the RGM executes the Stop method on node1 and the resource goes offline. In addition, during the execution of the Stop method on node1, the Oracle VM Server for SPARC guest domain is switched over to node2 using live migration in which case the Start method executed on node2 is a no-op.
A problem can occur if another resource group declares a strong negative (SN) affinity for the resource's group or if the RGM load limits are in use. In such a case, the guest domain actually migrates onto the target node before the RGM can evict any resource group or groups that need to be evicted due to strong negative affinities or load limits. Hence, there is a time interval in which the hard load limit or SN affinity is violated, resulting in overload of the node and consequent failure of the live migration attempt.
The following two features allow a data service that performs a switchover using live migration from the Stop method, to find out the target node of the switchover and to trigger any required resource group evictions caused by strong negative affinities or load limits before the switchover is initiated.
SCHA_TARGET_NODES query
Pre_evict resource property