If the input BO is handled by a single thread from end to end, the tuning for the edge components is normally adequate. In many situations, however, there are multiple thread switches during the end-to-end execution path. It is important to tune the system to ensure adequate concurrency for each asynchronous segment of the execution path.
Asynchronous invocations of a Service Component Architecture (SCA) component use an MDB to listen for incoming events that arrive in the associated input queue. Each SCA module defines an MDB and its corresponding activation specification (JNDI name: sca/module name/ActivationSpec).
The asynchrony in a long-running BPEL process occurs at transaction boundaries. BPE defines an internal MDB and its ActivationSpec: BPEInternalActivationSpec. If you use JMS navigation, rather then the default Work-Manager-based navigation, tune the maxConcurrency parameter using the same guidelines as for SCA module and JMS export MDBs.