Oracle Streams Advanced Queuing Leverages Oracle Database You can arrange transformations to occur when a message is enqueued, when it is dequeued, or when it is propagated to a remote subscriber. The transformation is represented by a SQL function that takes the source data type as input and returns an object of the target data type. A transformation defines a mapping from one data type to another. Or many producers enqueue messages, each message being processed by a different consumer depending on type and correlation identifier.Įnqueued messages are said to be propagated when they are reproduced on another queue, which can be in the same database or in a remote database.Īpplications often use data in different formats. Messages can be enqueued without being dequeued.Īt a slightly higher level of complexity, many producers enqueue messages into a queue, all of which are processed by one consumer. Messages are not necessarily dequeued in the order in which they are enqueued. Producers can enqueue messages in any sequence. An agent program or application may act as both a producer and a consumer. Likewise, a consumer may wait when trying to dequeue a message if no message is available. A producer may stipulate a delay before the message is available to be consumed, and a time after which the message expires. A message stays in the queue until a consumer dequeues it or the message expires. Each message is dequeued and processed once by one of the consumers. At the most basic level of queuing, one producer enqueues one or more messages into one queue.
When Web-based business applications communicate with each other, producer applications enqueue messages and consumer applications dequeue messages.
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