DESCRIPTION: DDS_ResourceLimitsQosPolicy::max_instances limits the maximum number of instances a DDS_DataReader can manage. Instance state is one of the most expensive resources to maintain as well as often being the highest one.

: The resources allocated by an instance is normally only released when an instance is disposed and all known owners have unregistered the instance, please refer to FooDataWriter_unregister_instance and FooDataWriter_dispose.

: The DDS_DataReaderResourceLimitsQosPolicy::instance_replacement policy is useful to maintain state for only the last N instances and when it is not necessary to keep samples in the DDS_DataReader history cache. When the DDS_DataReaderResourceLimitsQosPolicy::instance_replacement policy is set to replace the oldest instance (DDS_REPLACE_OLDEST_INSTANCE_REPLACEMENT_QOS), information about the oldest instance is automatically removed and the newly discovered instance is received. The disadvantage is that DDS_NOT_ALIVE_NO_WRITERS_INSTANCE_STATE state cannot be maintained. The DDS_NOT_ALIVE_DISPOSED_INSTANCE_STATE is maintained for an instance that is accepted (either there is space or another instance is replaced), regardless of whether any samples have previously been received.

SEE ALSO: DDS_DataReaderResourceLimitsInstanceReplacementKind instance_replacement