QoSs

When a persistence service discovers a topic 'A' that matches a specific persistence group, it creates a reader (known as ‘PRSTDataReader’) and writer (‘PRSTDataWriter’) to persist that topic. The QoSs associated with these readers and writers, as well as the corresponding publishers and subscribers, can be configured inside the persistence group using QoS tags.

For example:

<participant name="Part1">
    <domain_id>71</domain_id>
    <persistence_group name="PerGroup1" filter="*">
         ...
        <publisher_qos base_name="QosLib1::PubQos1"/>
        <subscriber_qos base_name="QosLib1::SubQos1"/>
        <datawriter_qos base_name="QosLib1::WriterQos1"/>
        <datareader_qos base_name="QosLib1::ReaderQos1"/>
	  ...
    </persistence_group>
</participant>

For instance, the number of DDS samples saved by Persistence Service is configurable through the HISTORY QosPolicy of the PRSTDataWriters.

If a QoS tag is not specified the persistence service will use the corresponding DDS default values (DurabilityService QoS Policy describes an exception to this rule).

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