Rollbacks not working as desired with nonBlockingInvoke

Hello,

We need some guidance on transaction boundaries and rollbacks in a BPEL process that calls a DB and an external Web Service.  Here's the setup.

We have a Web Service - let's call it "MyLoggingService" - which is a synchronous Web Service (SOAP service which calls a Mediator).  The purpose of this services is to simply log audit information (request payloads, response payloads, fault payloads, etc.).

We have a BPEL process - let's call it "MyBPELProcess" - which stores business data in the database and, secondarily, logs a bunch of audit payloads to MyLoggingService (request, response, fault, etc.).

Although MyLoggingService is synchronous, we don't want to wait for it's reply (we don't care if the data got logged, nor do we want the BPEL instances processing time to include the logging time).  Essentially, we want to call MyLogingService in a non-blocking, fire-and-forget manner.