Durable and Non-Durable Subscriptions

Subscribers to a topic destination have either durable or non-durable subscriptions. Durable subscriptions provide increased reliability at the cost of slower throughput for the following reasons:

• The Message Queue message server must persistently store the list of messages assigned to each durable subscription so that should a message server fail, the list is available after recovery.

• Persistent messages for durable subscriptions are stored persistently, so that should a message server fail, the messages can still be delivered after recovery, when the corresponding consumer becomes active. By contrast, persistent messages for non-durable subscriptions are not stored persistently (should a message server fail, the corresponding consumer connection is lost and the message would never be delivered).

For nonpersistent messages, performance is about the same for durable and non durable subscriptions. For persistent messages, performance is about 20% lower for durable subscriptions than for nondurable subscriptions.