How does JMS "Exactly Once Notification" work?

Hi All,

We have a situation where a (non webMethods) client sends a message via JMS queue and if it doesn’t receive a response within certain time, it retries.

On webMethods side, I was exploring the option of using exactly Once Notification. But the document doesn’t mention much on it.

How does IS/JMS adapter identify duplicate document?
What happens if a document is duplicate? Does it stay in queue?