About Message Modes

Oracle Streams Advanced Queuing (AQ) supports the following message modes:

• Persistent messaging: Messages are always stored on disk in a database table called a queue table. This type of storage is sometimes called persistent queue storage.

• Buffered messaging: Messages are stored in memory but can spill to a queue table under certain conditions. This type of storage is sometimes called buffered queue storage.

Buffered messaging provides better performance, but it does not support some messaging features, such as message retention. Message retention lets you specify the amount of time a message is retained in the queue table after being dequeued. In addition, when a database goes down unexpectedly, persistent messages are retained on disk, but buffered messages can be lost because they are stored in memory.

Message retention provides an audit trail, which might be required for some organizations. For example, while messages are stored in the queue table, users and applications can run queries to gather information about the messages. For example, a sales application might gather this information to generate a report on orders.