Use of Transactions

A transaction is a guarantee that all messages produced in a transacted session and all messages consumed in a transacted session will be either processed or not processed (rolled back) as a unit.

Message Queue supports both local and distributed transactions.

A message produced or acknowledged in a transacted session is slower than in a nontransacted session for the following reasons:

• Additional information must be stored with each produced message.

• In some situations, messages in a transaction are stored when normally they would not be (for example, a persistent message delivered to a topic destination with no subscriptions would normally be deleted, however, at the time the transaction is begun, information about subscriptions is not available).

• Information on the consumption and acknowledgment of messages within a transaction must be stored and processed when the transaction is committed.

To improve performance, Message Queue message brokers are configured by default to use a memory-mapped file to store transaction data. On file systems that do not support memory-mapped files, you can disable this behavior by setting the broker property imq.persist.file.transaction.memorymappedfile.enabled to false.