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You should define each agent that you will use to communicate events in the Event Manager. Each agent's name must be unique within its system. The agent can be referenced in code within Oracle Workflow by a compound name in the following format:

<agent_name>@<system_name>

For example, the agent WF_IN within the system HUB could be referenced as WF_IN@HUB.

After defining the agents on your local system, you should set them up for event message propagation by scheduling listeners for local inbound agents and propagations for local outbound agents. See: Scheduling Listeners for Local Inbound Agents and Scheduling Propagations for Local Outbound Agents.

Assigning a Direction to an Agent

Assigning a Protocol to an Agent

A protocol can represent a network standard, such as SQLNET. It can also represent a business-to-business standard that defines the higher-level message format and handshaking agreements between systems in addition to the network standard.

The Business Event System interacts with an agent through an AQ queue. You can use AQ to perform the propagation of messages by the SQLNET protocol which it supports. In Oracle9i, AQ also includes Internet access functionality that lets you perform AQ operations over the Internet by using AQ's Internet Data Access Presentation (IDAP) for messages and transmitting the messages over the Internet using transport protocols such as HTTP or HTTPS. Additionally, the Messaging Gateway feature of AQ in Oracle9i enables communication between applications based on non-Oracle messaging systems and AQ, letting you integrate with third party messaging solutions. You can also implement other services to propagate messages by different protocols. The following table shows which services you can use for various protocols, depending on your database version.

To implement a custom protocol, you must perform the following steps:

• 1. Define AQ queues to hold pending inbound and outbound messages.

• 2. Provide code that propagates messages to and from the AQ queues.

• 3. Define a lookup code for the new protocol in the Event Protocol Type (WF_AQ_PROTOCOLS) lookup type, which is stored in the Standard item type. The Event Manager uses the Event Protocol Type lookup type to validate the protocol for an agent. See: To Create Lookup Codes for a Lookup Type.

• 4. Define agents with the new protocol. See: To Define an Agent.

If an agent supports inbound communication, you must specify the address by which systems can communicate with it. The format of the address depends on the agent's protocol. For agents that use the SQLNET protocol, the address must be in the following format to enable AQ propagation:

<schema>.<queue>@<database link>

In this format, <schema> represents the schema that owns the queue, <queue> represents the queue name, and <database link> represents the name of the database link to the instance where the queue is located.

Note: You must enter the database link name exactly as the name was specified when the database link was created. For example, if a database link is named ORA816.US.ORACLE.COM, you must enter that complete name in the address of an agent on that database. You cannot abbreviate the name to ORA816.

The names of the database links that you want to use for the Business Event System should be fully qualified with the domain names. To confirm the names of your database links, use the following syntax:

      SELECT db_link FROM all_db_links

See: Creating Database Links.

Assigning a Queue to an Agent

Event messages within the Oracle Workflow Business Event System are encoded in a standard format defined by the datatype WF_EVENT_T. You must assign each agent a PL/SQL package called a queue handler that translates between this standard Workflow format and the format required by the agent's queue. See: Event Message Structure.

Note: Even if the agent's queue uses WF_EVENT_T as its payload type, a queue handler is still required in order to set native AQ message properties.

Oracle Workflow provides two standard queue handlers, called WF_EVENT_QH and WF_ERROR_QH, for queues that use SQLNET propagation and use the WF_EVENT_T datatype as their payload type. You can use WF_EVENT_QH with queues that handle normal Business Event System processing, while WF_ERROR_QH should be used exclusively with error queues.

Oracle Workflow also provides a queue handler called WF_EVENT_OMB_QH, which you can use if you implement Oracle Message Broker with Oracle8i to propagate messages between systems by another protocol such as HTTP. See: Setting Up the WF_EVENT_OMB_QH Queue Handler and Mapping Between WF_EVENT_T and OMBAQ_TEXT_MSG.

If you want to use queues that require a different format, create a custom queue handler for that format. Your custom queue handler must include a set of standard APIs to enqueue and dequeue messages in the custom format. See: Standard APIs for a Queue Handler.

Standard Agents

These agents use standard queues that are automatically defined when you install Oracle Workflow. See: Setting Up Queues.

You can enable or disable the WF_IN and WF_OUT agents, but you must not make any other changes to their definitions. You must not make any changes to the definitions of the WF_DEFERRED and WF_ERROR agents.

However, you must schedule listeners for the WF_DEFERRED and WF_ERROR agents to enable deferred subscription processing and error handling for the Business Event System, respectively. Also, if you want to use the WF_IN and WF_OUT agents for event message propagation, schedule a listener for WF_IN and propagations for WF_OUT as well. See: Scheduling Listeners for Local Inbound Agents and Scheduling Propagations for Local Outbound Agents.

Additionally, a standard agent named WF_SMTP_O_1_QUEUE is defined for the Notification Mailer SMTP queue. This agent appears in the Check Setup page and the Event System Local Queues page, enabling you to use these pages to check the number of notification messages on the Notification Mailer queue. The WF_SMTP_O_1_QUEUE agent is not used by the Business Event System, however, so its status is Disabled and no queue handler is defined for it. You must not run an agent listener for this agent. See: Implementing the Notification Mailer, Checking the Business Event System Setup, and Reviewing Local Queues.

The following table lists the default properties for the standard WF_IN agent.

The following table lists the default properties for the standard WF_OUT agent.

The following table lists the default properties for the standard WF_DEFERRED agent.

The following table lists the default properties for the standard WF_ERROR agent.

The following table lists the default properties for the standard WF_SMTP_O_1_QUEUE agent.

See Also

To Find Agents

To Update or Delete an Agent

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