Message stores play an essential part in the operation of messaging engines. Each messaging engine has one and only one message store, which can be either a file store or a data store.
A message store enables a messaging engine to preserve operating information and to retain those objects that messaging engines need for recovery in the event of a failure.
A messaging engine preserves both volatile and durable data in its message store. Volatile data is lost when a messaging engine stops, in either a controlled or an uncontrolled manner. Durable data is available after the server restarts. For more information, refer to Message reliability levels. A messaging engine stores various types of data, including messages, transaction states, and communication channel states.
When started, a messaging engine obtains configuration information from the WebSphere Common Configuration Model (WCCM) repository. A messaging engine retrieves all other data from its own file store or data store.