PowerHA failover and failback

If a node fails, the server cluster transfers the groups that were being hosted by the node to other nodes in the cluster. This transfer process is called failover. The reverse process, failback, occurs when the failed node becomes active again and the groups that were failed over to the other nodes are transferred back to the original node.

The terms production node and standby node refer to the two PowerHA® nodes on which the Tivoli® Storage Manager server runs.

PowerHA manages taking over the TCP/IP address and mounting the shared file system on the standby node or production node, as appropriate.

When a failover or failback occurs, any transactions that were being processed at the time are rolled back. To Tivoli Storage Manager clients, failover or failback represents a communications failure. Therefore, you must reestablish a connection that is based on their COMMRESTARTDURATION and COMMRESTARTINTERVAL option settings.

Typically, you can restart the backup-archive client from the last committed transaction. If a client schedule is running when a failover occurs, the client operation is likely to fail. If you can restart client operations, then you must restart them from the beginning of the processing. The clients and agent operations complete as they normally do if the server was halted and restarted while they were connected. The only difference is that the server is physically restarted on different hardware.

If you do not want automatic failback to occur, you can configure the resource as a cascading resource group without failback.