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Advanced Queuing - Oracle

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XMLType Payloads<br />

General Features of <strong>Advanced</strong> <strong>Queuing</strong><br />

information is used to partition the queue tables between instances for<br />

queue-monitor scheduling. The queue table is monitored by the queue monitors of<br />

the instance specified by the user. If an instance affinity is not specified, the queue<br />

tables is arbitrarily partitioned among the available instances. There can be pinging<br />

between the application accessing the queue table and the queue monitor<br />

monitoring it. Specifying the instance affinity does not prevent the application from<br />

accessing the queue table and its queues from other instances.<br />

This feature prevents pinging between queue monitors and <strong>Advanced</strong> <strong>Queuing</strong><br />

propagation jobs running in different instances. If compatibility is set to <strong>Oracle</strong>8i,<br />

release 8.1.5 or higher, an instance affinity (primary and secondary) can be specified<br />

for a queue table. When <strong>Advanced</strong> <strong>Queuing</strong> is used with Real Application Clusters<br />

and multiple instances, this information is used to partition the queue tables<br />

between instances for queue-monitor scheduling as well as for propagation. At any<br />

time, the queue table is affiliated to one instance. In the absence of an explicitly<br />

specified affinity, any available instance is made the owner of the queue table. If the<br />

owner of the queue table is terminated, the secondary instance or some available<br />

instance takes over the ownership for the queue table.<br />

To see this feature applied in the context of the BooksOnLine scenario, refer to<br />

"Support for <strong>Oracle</strong> Real Application Clusters" on page 8-30.<br />

You can create queues that use the new opaque type, XMLType. These queues can<br />

be used to transmit and store messages that are XML documents. Using XMLType,<br />

you can do the following:<br />

Store any type of message in a queue<br />

Store documents internally as CLOBs<br />

Store more than one type of payload in a queue<br />

Query XMLType columns using the operators ExistsNode() and<br />

<br />

SchemaMatch()<br />

Specify the operators in subscriber rules or dequeue conditions<br />

Internet Integration and Internet Data Access Presentation<br />

You can access AQ over the Internet by using Simple Object Access Protocol<br />

(SOAP). Internet Data Access Presentation (IDAP) is the SOAP specification for AQ<br />

operations. IDAP defines the XML message structure for the body of the SOAP<br />

request. An IDAP-structured message is transmitted over the Internet using<br />

Introduction to <strong>Oracle</strong> <strong>Advanced</strong> <strong>Queuing</strong> 1-11

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