An Activation Spec is used to configure the message delivery to an MDB. The ejb-jar.xml deployment descriptor needs to include a <activation-config> element inside the <message-driven> element like:

<activation-config>
    <activation-config-property>
       <activation-config-property-name>destination</activation-config-property-name>
       <activation-config-property-value>queue.testQueue</activation-config-property-value>
    </activation-config-property>
    <activation-config-property>
       <activation-config-property-name>destinationType</activation-config-property-name>
       <activation-config-property-value>javax.jms.Queue</activation-config-property-value>
    </activation-config-property>
</activation-config>

Here, the value for destination is the physical name of the desired destination. The value for destinationType is the class name that defines the type of destination. It should be javax.jms.Queue or javax.jms.Topic.
 

The Activation Spec properties that can be configured are:

Property Name Required Default Value Description
acknowledgeMode no Auto-acknowledge The JMS Acknowledgement mode to use. Valid values are: Auto-acknowledge or Dups-ok-acknowledge
clientId no set in resource adapter The JMS Client ID to use (only really required for durable topics)
destinationType yes null The type of destination; a queue or topic
destination yes null The destination name (queue or topic name)
enableBatch no false Used to enable transaction batching for increased performance
maxMessagesPerBatch no 10 The number of messages per transaction batch
maxMessagesPerSessions no 10 This is actually the prefetch size for the subscription. (Yes, badly named).
maxSessions no 10 The maximum number of concurrent sessions to use
messageSelector no null The JMS Message Selector to use on the subscription to perform content based routing filtering the messages
noLocal no false Only required for topic subscriptions; indicates if locally published messages should be included in the subscription or not
password no set in resource adapter The password for the JMS connection
subscriptionDurability no NonDurable Whether or not a durable (topic) subscription is required. Valid values are: Durable or NonDurable
subscriptionName no null The name of the durable subscriber. Only used for durable topics and combined with the clientID to uniquely identify the durable topic subscription
userName no set in resource adapter The user for the JMS connection
useRAManagedTransaction no false Typically, a resource adapter delivers messages to an endpoint which is managed by a container. Normally, this container likes to be the one that wants to control the transaction that the inbound message is being delivered on. But sometimes, you want to deliver to a simpler container system that will not be controlling the inbound transaction. In these cases, if you set useRAManagedTransaction to true, the resource adapter will commit the transaction if no exception was generated from the MessageListener and rollback if an exception is thrown.
initialRedeliveryDelay no 1000 The delay before redeliveries start. Also configurable on the ResourceAdapter
maximumRedeliveries no 5 The maximum number of redeliveries or -1 for no maximum. Also configurable on the ResourceAdapter
redeliveryBackOffMultiplier no 5 The multiplier to use if exponential back off is enabled. Also configurable on the ResourceAdapter
redeliveryUseExponentialBackOff no false To enable exponential backoff. Also configurable on the ResourceAdapter

Maximising Throughput of MDBs

If you want to maximise throughput of MDBs you should really set the maxSessions to something fairly large to increase the concurrency. Then set maxMessagesPerSessions to something big (say) 1000.

This assumes you have large numbers of messages available (say more than maxSessions * maxMessagesPerSession). Otherwise the prefetch will end up starving other consumers.

So if you don't have that many messages available, but maybe they take a while to process then you might want to set a lower value of maxMessagesPerSessions