OracleAQMessageDeliveryMode Enumeration

Buffered

Indicates a buffered message.

Both enqueue and dequeue buffered messaging operations must be in IMMEDIATE visibility mode. This means that these operations cannot be part of another transaction. You cannot specify delay when enqueuing buffered messages.

Dequeuing applications can choose to dequeue persistent messages only, buffered messages only, or both types.

Buffered messages can be queried using the AQ$Queue_Table_Name view. These messages appear with states, IN-MEMORY or SPILLED.

Buffered messaging is supported in Oracle Database 10g release 2 (10.2) and higher releases. Recipient lists are supported for buffered messaging.

Buffered messaging is supported in all queue tables created with a database compatibility level of 8.1 or higher. Transaction grouping queues and array enqueues are not supported for buffered messages in Oracle Database 11g release 1 (11.1) . One can still use the array enqueue procedure to enqueue buffered messages, but the array size must be set to 1. Array dequeue is not supported for buffered messaging, but one can still use the array dequeue procedure by setting array size to 1.

Buffered messaging is faster than persistent messaging. Use buffered messaging for applications that do not require the reliability and transaction support of Oracle Streams AQ persistent messaging.

Persistent

Indicates a persistent message.

Persistent messaging ensures reliability and support transactions. It is slower than buffered messaging.

PersistentOrBuffered

Indicates a persistent or buffered message.

This is used with Dequeue() when a consumer wants to dequeue a message irrespective of whether it is Persistent or Buffered.