activemq的一点疑问

Question

<!-- Destination specific policies using destination names or wildcards -->
        <destinationPolicy>
            <policyMap>
                <policyEntries>
                    <policyEntry queue=">" memoryLimit="5mb"/>
                    <policyEntry topic=">" memoryLimit="5mb">
                      <!-- you can add other policies too such as these
                        <dispatchPolicy>
                            <strictOrderDispatchPolicy/>
                        </dispatchPolicy>
                        <subscriptionRecoveryPolicy>
                            <lastImageSubscriptionRecoveryPolicy/>
                        </subscriptionRecoveryPolicy>
                      -->
                    </policyEntry>
                </policyEntries>
            </policyMap>
        </destinationPolicy>这里配的是缓存吧   如果缓存慢了  后面发过来的消息又该如何处理？