|Maximum duration for the data's validity. |
Each data sample written by the DDSDataWriter has an associated expiration time beyond which the data should not be delivered to any application. Once the sample expires, the data will be removed from the DDSDataReader caches as well as from the transient and persistent information caches.
The expiration time of each sample from the DDSDataWriter's cache is computed by adding the duration specified by this QoS policy to the sample's source timestamp. The expiration time of each sample from the DDSDataReader's cache is computed by adding the duration to the reception timestamp.
DDS_HistoryQosPolicy), the total amount of data it stores may be limited by this QoS policy.
You may also use this QoS policy to ensure that applications do not receive or act on data, commands or messages that are too old and have 'expired.'
To avoid inconsistencies, multiple writers of the same instance should have the same lifespan.