Durable Prefetch Count
The prefetch count parameter of a durable limits the number of messages per batch that the durable can deliver to a subscriber. This value affects delivery performance.
Positive integer values enable prefetch, and determine the maximum batch size. Zero disables prefetch, however, zero is a legal value only for standard durables.
Appropriate values for prefetch count depend on the use case.
For standard durables that will back a direct path, set this parameter to zero for best performance. (Standard durables are already optimized for direct path delivery without prefetch.)
For standard durables that will deliver messages in the absence of a direct path, set this parameter to a non-zero starting value of 1024. You can tune this parameter to optimize delivery speed. If the durable's message backlog grows, try increasing this value. If the subscriber is overloaded and discards messages, try decreasing this value.
For last-value durables, you can tune this parameter to control the flow of messages from a fast publisher.
With wide-area stores, the best practice is non-zero prefetch with either shared durables or standard durables.