I have two BizTalk 2010 servers that belong to the same BizTalk group. They are being used to expose a web service front-end to SAP BAPI calls. A load balancer sits in front of the two BizTalk servers for the web service requests. If both BizTalk servers are active, I get session errors when calling BAPIs that modify data. The first call on the first server succeeds, but a second call that is serviced by the other server fails with a session error when the BAPI_COMMIT_TRANSACTION message is sent to SAP. This also has the side-effect of leaving an open transaction in SAP and locking the records.
Has anybody else seen this behavior? Is the WCF-SAP adapter limited to only one active instance like the FTP adapter?