The sensor will store the alert and packet log info in the event the manager is not available. The sensor will continue to process traffic as it normally would.
Here is an entry from the CLI guide and KB that is in the process of being updated for the newer model info:
In the event that connectivity between the Sensor and the Manager is interrupted, the Sensor saves
alert data internally. This data is sent to the Manager when connectivity is re-established and the
internal information is deleted. This command shows the number of alerts and packet logs that have
been saved within the Sensor.
Information displayed by the show savedalertinfo command includes:
• Whether a file of saved alerts exists (if connectivity between Sensor and Manager is currently
established, no file will exist)
• Number of saved alerts and their size
• Whether a file of saved packet logs exists
• Number of saved packet logs and their size
This command has no parameters.