Summary

Windows DNA provides several ways for three-tier distributed applications based on COM and MTS to interoperate with applications and resources on non-Windows platforms. When transactional interoperability is not required, COM can be used to wrap access to applications within COM components. DCOM is used as the communications mechanism between the Windows machine and the non-Windows machine. If transactional interoperability is required, the technology used depends on the transaction protocols supported by the transaction managers and resource managers. The MS DTC is able to interoperate with many XA-compliant resource managers through ODBC drivers that map OLE Transactions calls into XA calls. The MS DTC also provides a mapping layer that lets XA-compliant transaction managers use OLE Transactions resource managers. Interoperability with LU 6.2_based TP-Monitors such as IBM CICS and IMS is accomplished using the COMTI.

Message queuing is another option for interoperability. In this case, messages are passed from the Windows machine to the non-Windows machine. The messages are interpreted by custom code running on the destination machine. Message queuing can also be used to build time-independent applications.

We will discuss how to develop applications using MSMQ and COMTI in detail in Chapter 15.