B2B Integration : A Practical Guide to Collaborative E-commerce

Middleware Technologies 227
Program A makes an MQPUT call specifying not a local queue but
a local definition of a remote queue. This definition identifies a queue
on another queue manager. The queue manager to which Program A is
connected puts the message on a special queue called a transmission
queue. The message is then automatically sent along the channel
connecting the two queue managers. The receiving queue manager puts
the message on the queue that was originally specified by Program A.
This message is stored on the queue until it is retrieved by Program B,
after Program B has issued an MQGET call.
MQSeries can support three kinds of transactional operations as
follows:
• Internal Transactions — MQSeries supports internal operations and
transactions related to the actual messages. Messages are managed
using transactional controls, allowing it to commit or rollback/resubmit
messages in the event of a failure. In that case, all messages would
rollback and the original input message would be reinstated on the
queue.
• External Transactions — MQSeries supports external transactional
managers, such as TP monitors. MQSeries can commit or rollback all
message processing, based upon the success or failure of the external
transaction. In the event of a failure, all messages would rollback and
the original message would be reinstated on the queue. In this mode,
MQSeries is acting as a so-called resource manager. MQSeries can
integrate with any X/Open XA compliant transaction manager, such
as BEA Tuxedo and IBM's CICS.
• Self Transactional — MQSeries can act as a transaction manager,
managing messaging and other X/Open XA-compliant resources, such
as databases. This allows MQSeries to support transactions without
the use of a TP monitor or application server. MQSeries does not
provide all the capabilities of an enterprise TP monitor, but it can be
a good fit where a need for transaction management is at a minimum.
MQSeries provides intelligent routing, allowing servers to forward
messages along the shortest path available. Intelligent routing will
also route messages around networks which have failed or which are
experiencing problems.