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When you schedule a listener for an agent, it monitors the agent's queue, dequeuing any inbound event messages. When an event message is received, the Event Manager searches for and executes any enabled subscriptions by the local system to that event with a source type of External, and also any enabled subscriptions by the local system to the Any event with a source type of External. The listener exits after all event messages on the agent's queue have been dequeued.

The PL/SQL and Java agent listener programs are defined as service component types in the Generic Service Component Framework. This framework helps to simplify and automate the management of background Java services.

You can use Oracle Workflow Manager to submit and manage agent listener service components. You can also view the distribution of event messages on different agents, drill down to view details about individual event messages, and review queue details for the agents. Oracle Workflow Manager is available as a component of Oracle Applications Manager if you are using the version of Oracle Workflow embedded in Oracle Applications, or as a component of Oracle Enterprise Manager if you are using the standalone version of Oracle Workflow. For more information, please refer to the Oracle Applications Manager online help or the Oracle Enterprise Manager online help.

Oracle Workflow also provides an administrative script named wfagtlst.sql that you can use to run a PL/SQL agent listener. See Wfagtlst.sql.

Oracle Workflow provides seeded PL/SQL agent listener service components for the standard WF_DEFERRED, WF_ERROR, and WF_NOTIFICATION_IN agents. These agent listeners are named Workflow Deferred Agent Listener, Workflow Deferred Notification Agent Listener, Workflow Error Agent Listener, and Workflow Inbound Notifications Agent Listener, and they support deferred subscription processing in the database, dedicated deferred subscription processing for notification messages, error handling for the Business Event System in the database, and inbound e-mail processing for notification mailers, respectively.

In Oracle Applications, Oracle Workflow provides seeded Java agent listener service components for the standard WF_JAVA_DEFERRED, WF_JAVA_ERROR, and WF_WS_JMS_IN agents. These agent listeners are named Workflow Java Deferred Agent Listener, Workflow Java Error Agent Listener, and Web Services IN Agent, and they support deferred subscription processing in the middle tier, error handling for the Business Event System in the middle tier, and inbound Web service message processing, respectively.

In Oracle Applications, Oracle XML Gateway also provides two seeded PL/SQL agent listener service components for the standard ECX_INBOUND and ECX_TRANSACTION agents. These agent listeners are named ECX Inbound Agent Listener and ECX Transaction Agent Listener, respectively. For more information, see Starting Agent Listeners, Oracle XML Gateway User's Guide. See: Monitor Workflow Processes, Oracle XML Gateway User's Guide.

You can also optionally create additional agent listener service components. For example, you can configure agent listeners for other inbound agents that you want to use for event message propagation, such as the standard WF_IN and WF_JMS_IN agents, or any custom agents. You can also configure an agent listener service component that only processes messages on a particular agent that are instances of a specific event.

Service components must be hosted by a service component container. If you create custom agent listener service components, you can assign them to the seeded container for agent listeners.

• In Oracle Applications, a service component container is implemented as a Generic Service Management (GSM) service. The seeded container for agent listeners is named Workflow Agent Listener Service.

• In standalone Oracle Workflow, a service component container is implemented as a servlet within an OC4J instance. The seeded container for agent listeners is named WFALSNRSVC, within an OC4J instance named OC4J_Workflow_Component_Container.

Before agent listener service components can run, the container which manages them must first be started. In order to run the seeded agent listeners, you should ensure that the Workflow Agent Listener Service container is running using Oracle Applications Manager for the version of Oracle Workflow embedded in Oracle Applications, or ensure that the WFALSNRSVC container is running using Oracle Enterprise Manager for the standalone version of Oracle Workflow. If you create your own custom containers in OAM for custom service components, ensure that those containers are running as well.

Note: In Oracle Applications, you can run a diagnostic test to verify the GSM services for Oracle Workflow. See: Oracle Workflow Diagnostic Tests.

See Also

Listen, Oracle Workflow API Reference

Wfagtlst.sql