WebSphere MQ messages
WebSphere MQ messages
•
WebSphere MQ messages are made up of two
parts:
•
1. Message descriptor
•
2. Application data
Message descriptor
•
You can access message control information
using the MQMD structure.
Types of message
•
There are four types of message defined by
WebSphere MQ:
•
Datagram
•
Request
•
Reply
•
Report
Datagrams
•
Use a datagram when you do not require a
reply from the application that receives the message (that is, gets the message
from the queue).
•
An example of an application that could use
datagrams is one that displays flight information in an airport lounge. A
message could contain the data for a whole screen of flight information.
Request messages
•
Use a request message when you want a
reply from the application that receives the message.
Reply messages
•
Use a reply message when you reply to
another message.
•
When
you create a reply message, respect any options that were set in the message
descriptor of the message to which you are replying.
Report messages
•
Report messages inform applications
about events such as the occurrence of an error when processing a message. They
can be generated by:
•
A
queue manager,
•
A
message channel agent (for example, if they cannot deliver the message), or
•
An application (for example, if it cannot use
the data in the message).
Types of Report messages
•
Exception report message.
•
This is sent in response to a message with the
exceptions flag set
•
Expiry report message.
•
This indicates that an application attempted
to retrieve a message that had reached its expiry threshold.
•
confirmation of arrival (COA) report
message
•
This indicates that the message has reached
its target queue
•
Confirmation of delivery (COD) report
message.
•
This indicates that the message has been
retrieved by a receiving application
•
Negative action notification (NAN)
report message. This indicates that a request has not been successfully
serviced
Tags: Message queuing, MQ, Webshpere
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