user manual

220 BES Developer’s Guide

MDBs and transactions

See Chapter 23, “Using JMS” for information on using JMS within

transactions. This section deals exclusively with using MDBs in transactions.

The most common scenario of using MDBs in transactions is the desire to

have two-phase commit (2PC) completion of transactions started for the

onMessage() method. Such an MDB will have the REQUIRED transaction attribute.

However, if you have a Partition's 2PC transaction service running, then all

modules deployed to that Partition can discover it and attempt to use it. The

2PC engine will perform one-phase commit when only one resource is

registered, but it will suffer the RMI overhead of the 2PC engine when the

Partition's standard transaction manager would perform far better. To avoid

this possible waste of resources, you can add the following bean-level

property to the MDBs that require 2PC. Use the Console to navigate to the

module and Right-click it. Select DDEditor and select the required bean from

the Navigation Pane once the DDEditor appears. Click the Properties tab and

add this property. Define this property as a string:

ejb.transactionManagerInstanceName

For more information on 2PC and the transaction manager, go to Chapter 19,

“Transaction management”.

Note ejb.transactionManagerInstance is also supported for Entity and Session beans.