The Store-and-Forward (SAF) service enables WebLogic Server to deliver messages reliably between applications that are distributed across WebLogic Server instances. If the destination is not available at the moment the messages are sent, either because of network problems or system failures, then the messages are saved on a local server instance, and are forwarded to the remote destination once it becomes available. SAF agents are responsible for storing and then forwarding messages between local sending and remote receiving endpoints. A SAF agent can be configured to have only sending capabilities, receiving capabilities, or both. JMS SAF only requires a sending agent on the sending side for JMS messages. Whereas, WSRM SAF requires both a sending agent and a receiving agent.
In a clustered server environment, a SAF agent can targeted to a migratable target. A migratable target is a special target that can serve as a grouping of migratable JMS services, such as a SAF agent, and which is active on only server member in a WebLogic cluster. In a cluster, a recommended best practice is to target a SAF agent to a migratable target, so that a member server will not be a single point of failure. This way the SAF agent can be manually migrated from an unhealthy server onto a healthy server, either in the event of server crash or for scheduled maintenance.
For more information about JMS Message Unit-of-Order, see Using JMS Message Unit-of-Order.
Note: If a SAF agent is targeted to a migratable target, it cannot be targeted to any other targets, including an entire cluster.