Listeners are the Service Components with in Oracle Workflow.
Following are the types:
- Workflow Agent Listener: Process inbound messages on Business Event System agents in the database.
- Workflow Java Agent Listener : This is only Limited to E-Business Suite Only: This process inbound message on the Business Event System agents in the middle tier. An agent listener monitors a Business Event System agent for incoming messages and dequeues messages using the agent's queue handler. PL/SQL agent listeners process event subscriptions with a PL/SQL rule function in the database where as the Java agent listeners(Oracle E-Business Suite only) process event subscriptions with a Java rule function or subscription to events with a Java generate function in the middle tier.
Oracle Workflow provides the following seeded PL/SQL agent listeners:
- Workflow Deferred Agent Listener: Handles messages on WF_DEFERRED to support deferred subscription processing.
- Workflow Deferred Notification Agent Listener: Handles notification messages on WF_DEFERRED to support outbound notification processing.
- Workflow Error Agent Listener: Handles messages on WF_ERROR to support error handling for the Business Event System.
- Workflow Inbound Notifications Agent Listener: Handles messages on WF_NOTIFICATION_IN to support inbound e-mail notification processing.
Within Oracle E-Business Suite, Oracle Workflow provides the following seeded Java agent listeners:
- Workflow Java Deferred Agent Listener: Handles messages on WF_JAVA_DEFERRED to support deferred subscription processing in the middle tier.
- Workflow Java Error Agent Listener: Handles messages on WF_JAVA_ERROR to support error handling for the Business Event System in the middle tier
SOMETIMES LISTENERS MIGHT BE DOWN AND OUR WORKFLOW MIGHT NOT RUN. HOW TO IDENTIFY THIS AND MAKE THEN COME UP?
You should configure agent listeners to run by default in Oracle Applications even if you do not use Oracle Workflow.
Other modules such as Oracle Application Object Library and the directory service use the Business Event System for internal processing and enqueue messages on the WF_DEFERRED and WF_JAVA_DEFERRED agents.
You should run the Workflow Deferred Agent Listener and the Workflow Java Deferred Agent Listener to process these events and prevent the queues from growing too large causing performance issues. System Administrators need to ensure that these listeners are always running. Use the following navigation to check the status and start if they are down:
Oracle Applications Manager -> Workflow Manager -> Agent Listeners