Microsoft Transaction Server

Although stand-alone Web applications are gaining significant momentum as a business solution, browser-based products are also likely to appear as additions to existing enterprise systems. For many businesses, browser access to business systems represents a powerful new way to provide information to remote locations. These remote sites might consist of customers who need technical support, other offices within the same company that are not part of an existing wide-area network (WAN), or even employees who are telecommuting across a modem. Demand for access can easily strain existing enterprise hardware that was not originally selected with external connection in mind.

As an application begins to scale into hundreds or even thousands of users, system resources become the limiting factor. Internet lore is full of stories about sites that were unprepared for a high level of demand and had to be shut down the same day they debuted. That is where Microsoft Transaction Server (MTS) enters the picture.

MTS is designed to provide all the features necessary to efficiently use the resources of machines hosting business systems. In particular, MTS provides pooling for three key system resources: threads, objects, and ODBC connections. MTS also includes features such as transaction management, but this chapter will focus only on using MTS to scale your site.

MTS relies heavily on the creation of COM business objects to efficiently manage middle tier functionality. These COM objects can be created in any visual development tool that supports them, including Microsoft Visual Basic, Microsoft Visual C++, Microsoft Visual J++, and Microsoft Visual FoxPro, but all the business objects created in this chapter will be built in Visual Basic. The chapter does not attempt to teach the fundamentals of constructing Visual Basic business objects but focuses instead on special techniques required to use these components under MTS. Therefore, you should be familiar with the process of creating ActiveX DLL projects in Visual Basic 5.0 prior to using these techniques on your Web site.