Format of event messages

Event messages contain information about the event and its origin. Typically, these messages are processed by a system management application program tailored to meet the requirements of the enterprise at which it runs. As with all WebSphere MQ messages, an event message has two parts: a message descriptor and the message data.

• The message descriptor is based on the MQMD structure, which is defined in the WebSphere MQ Application Programming Reference manual.

• The message data is also made up of an event header and the event data. The event header contains the reason code that identifies the event type. Putting the event message, and any subsequent actions following that, do not affect the reason code returned by the MQI call that caused the event. The event data provides further information about the event.

When the conditions are met to generate an event message to be generated for a shared queue, the queue managers in the queue sharing group decide whether to generate an event message. Several queue managers can generate an event message for one shared queue, resulting in several event messages being produced. To ensure that a system can correlate multiple event messages from different queue managers, these event messages have a unique correlation identifier (CorrelId) set in the message descriptor (MQMD). For further details of the MQMD see Message descriptor (MQMD) in event messages.