On either the initiator or responder computer, the back-end LOB application routes a message to the MessagesFromLOB table of the BTARNDATA SQL Server database. BTARN uses a SQL adapter to move the message from the MessagesFromLOB table to the private process. For more information, see "SQL Adapter" in BizTalk Server 2009 Help.
You can choose to use a File adapter to submit service content to BTARN, instead of using the default SQL adapter. If you choose to use a File adapter, BTARN does not support attachments.