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Advanced Queuing - Oracle

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Converting Messages<br />

An AQ payload of type RAW is always mapped to an MGW_BASIC_MSG_T<br />

<br />

canonical message with a RAW body. MGW_BASIC_MSG_T.header is set to<br />

NULL. This never results in a message conversion failure.<br />

For inbound propagation, the following rules apply:<br />

An MGW_BASIC_MSG_T canonical message is mapped as follows:<br />

<br />

For a RAW body of size 32k, message conversion fails.<br />

For a TEXT body, message conversion fails.<br />

For a canonical message with both a TEXT and RAW body, message<br />

<br />

conversion fails.<br />

Converting MGW_BASIC_MSG_T AQ Payload Types<br />

For outbound propagation, the following rules apply:<br />

An AQ payload of type SYS.MGW_BASIC_MSG_T is always mapped to an MGW_<br />

<br />

BASIC_MSG_T canonical message.<br />

For a RAW body, if both small and large values are set, message conversion fails.<br />

For a TEXT body, if both small and large values are set, message conversion<br />

<br />

fails.<br />

For inbound propagation, the following rules apply:<br />

An MGW_BASIC_MSG_T canonical message is mapped directly. This never<br />

<br />

results in a message conversion failure.<br />

Using Transformations<br />

Messaging Gateway can use AQ message transformation to convert between an AQ<br />

queue payload and a gateway canonical type. After a transformation is created<br />

using the DBMS_TRANSFORM package, a Messaging Gateway administrator can use<br />

DBMS_MGWADM.ADD_SUBSCRIBER and DBMS_MGWADM.ALTER_SUBSCRIBER to<br />

configure a gateway subscriber to use the transformation.<br />

For outbound propagation, the transformation is invoked when the gateway agent<br />

dequeues messages from the AQ queue. For inbound propagation, the<br />

transformation is invoked when the gateway agent enqueues messages to the AQ<br />

queue.<br />

Messaging Gateway 18-31

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