Cluster resource group exit programs
In IBM® i high availability environments, cluster resource group exit programs are called after a cluster-related event for a CRG occurs and responds to the event.
An exit program is called when a CRG detects certain events, such as a new node being added to the recovery domain, or the current primary node failing. The exit program is called with an action code that indicates what the event is. Furthermore, the exit program has the capability to indicate whether to process the event or not. User-defined simply means the IBM i cluster technology does not provide the exit program. Typically the exit program is provided by the application or data replication provider. The exit program is the way a CRG communicates cluster events to the exit program provider. The exit program can perform the appropriate action based on the event, such as allowing a resource access point to move to another node. The exit program is optional for a resilient device CRG but is required for the other CRG types. When a cluster resource group exit program is used, it is called on the occurrence of cluster-wide events, including when:
- A node leaves the cluster unexpectedly.
- A node leaves the cluster as a result of the End Cluster Node (QcstEndClusterNode) API or Remove Cluster Node Entry (QcstRemoveClusterNodeEntry) API.
- The cluster is deleted as a result of the Delete Cluster (QcstDeleteCluster) API.
- A node is activated by the Start Cluster Node (QcstStartClusterNode) API.
- Communication with a partitioned node is re-established.
Exit programs are written or provided by cluster middleware IBM Business Partners and by cluster-aware application program providers.
For detailed information on the cluster resource group exit programs, including what information is passed to them for each action code, see Cluster Resource Group Exit Program in the cluster API documentation.