In TIBCO ActiveMatrix® Adapter for SAP 7.x, the inbound service could configure the thread count to enable multiple dispatchers to handle the message request simultaneously. The thread is not dedicated to the service but on the session. If two services that share the same session, they will share a thread pool that has to thread count equal to the total thread count of each service. 

For example:
Session A, Inbound Service 1, Thread count 1, Client Connection B
Session A, Inbound Service 2, Thread count 3, Client Connection B

In this example both services share the same session, and thread pool would be 4. If user does not limit the number of messages being sent by BW, then each service could potentially process 4 messages concurrently as long as the client connection supports that number of connections.

To let service running in the single thread mode, that service must have it's own session, and the thread count for that service must be 1.