The tmnxDiamSessionEvent notification is issued when something unusual happens while handling a Diameter session. [CAUSE] A Diameter session has experienced a problem. The session ID is indicated with the tmnxDiamAppSessionId. The associated Diameter application policy is indicated with the tmnxDiamAppPlcyApplication. What happened is indicated with the tmnxDiamNotifyEventId and the tmnxDiamAppTrapDescription. [EFFECT] The effect depends on the cause. For example: if a Diameter message could not be transmitted, session setup may fail. [RECOVERY] The recovery depends on the cause.