Message stores

Message stores are important in the operation of messaging engines. To host queue-type destinations, a messaging engine includes a message store where, if necessary, it can hold messages until consuming applications are ready to receive them, or preserve messages in case the messaging engine fails. Each messaging engine has one and only one message store. This can either be 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. See Message reliability levels - JMS delivery mode and service integration quality of service. 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 WCCM (WebSphere Application Server Common Configuration Model) repository. A messaging engine retrieves all other data from its own file store or data store.

Important: There are currently no facilities available for migrating from a data store to a file store.

Subtopics

• Relative advantages of a file store and a data store
  Decide whether to use a file store or a data store for our messaging engine, by considering the advantages of each type.
• File stores
  File stores use a file system to preserve operating information and to persist the objects that messaging engines need for recovery in the event of a failure.
• Data stores
  A data store is a message store that uses a relational database. A messaging engine uses a data store to store operating information in the database, as well as to preserve essential objects that the messaging engine needs for recovery in the event of a failure.
• Message store high availability
  High availability is achieved by failing over messaging engines between servers. Both file stores and data stores can be deployed in a highly available environment.