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Writing system management applications
Brokers communicate with their neighbors in the hierarchy to establish the topology, and to inform their neighbors about the streams they support. They do this by publishing broker administration messages, as retained messages, using the WebSphere MQ Programmable Command Format (PCF).
Note that the format of administration information (including metatopics) might be changed in future products.
A PCF message starts with an MQCFH structure, which includes a definition of the type of command the message represents. This is followed by a succession of MQCFIN (integer parameter) and MQCFST (string parameter) structures. The PCF format is described in WebSphere MQ Programmable Command Formats and Administration Interface. The WebSphere MQ administration interface (MQAI) has been provided to help you write PCF applications. It is also described in WebSphere MQ Programmable Command Formats and Administration Interface.
The SYSTEM.BROKER.ADMIN.STREAM queue is used for broker administration messages. System management applications can subscribe to these messages, provided that they have the correct security authorization. Subscription requests for these topics are sent to the SYSTEM.BROKER.CONTROL.QUEUE in the normal way.
Topics starting 'MQ/' are reserved for WebSphere MQ use, but other topics can be defined. The broker passes these publications to subscribers in the same way as for other streams.
Brokers publish on the 'MQ/QMgrName/Children' and 'MQ/QMgrName/Parent' topics if applicable. This enables applications to build a view of the broker topology.
The 'MQ/QMgrName/StreamSupport' topic is published on by all brokers. This enables applications to build a view of the stream topology in relation to the broker topology.
Brokers also publish messages to this queue when a stream or broker has been deleted, and when a subscription has been deregistered by the broker because it is no longer valid.
This chapter discusses the following topics:
Metatopics are published on the stream to which they relate so the relevant ones are published on SYSTEM.BROKER.ADMIN.STREAM. For information about metatopics see Metatopics.
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