7.5.4 Transaction affinity
When several requests to EJB methods occur in the scope of the same transaction (a user-managed transaction or a container-managed transaction), all requests will go to the same cluster member, if possible. As soon as the WLM plug-in notices that a transaction is started, it stops dispatching the requests to different cluster members. All requests within the scope of this transaction are sent to the same cluster member.
Transaction affinity overwrites all other server selection policies.