When MTS introduced, the only resource manager supported was SQL Server (MSDTC and OLE Transaction Resource Managers).
In version 2.0, MSDTC is still the Transaction Manager, and it still uses OLE Transaction protocol. However, a specification has been written to allow MTS to support X/Open Resource Managers using X/' protocol.
One of the changes to Microsoft Internet Information Server version 4.0 (IIS) is the integration of Active Server Pages (ASP) technology and Microsoft Transaction Server (MTS.) The ASP technology built into IIS makes it possible to apply the client-server model to Web-based applications. It means faster responses to queries and less network traffic.
Under nS, ASP functionality has been extended further to accommodate scalable three-tier applications. Active Server Pages are now based on MTS. It means individual pages can be declaratively transactional and ASP applications can run in separate address spaces for reliability and security. Transactions cannot span pages; this is not usually good practice in a scalable application since it dictates that the server would need to keep state over multiple user interactions.
In IIS, each subtree of pages defined as an application can run either in the main IIS process (Inetinfo.exe) or in a particular MTS process (Mtx.exe). Process Isolation can be used to run a test or for staging version of new applications separately from the stable applications. Each server can run a combination of isolated and non-isolated applications.
The ability of the Webmaster to control how and where applications run means new versions of COM components or the IS API DLL could be loaded without stopping the entire Web server.
Since these types of separate applications based on MTS, they benefit from the reliability features of MTS. It means these apps will restart automatically after a component-based failure.
All of the Internet Server Application Programming Interface (ISAPI) management and Active Server Pages (ASP) code moved into a component called the Web Application Manager (WAM). Each application given a Globally Unique Identifier (GUID), and the WAMs registered as MTS components. Each application is a unique object.
IIS applications that are declared to run in-process registered in the MTS default in-process package. It is referred to in the MTS snap-in as “IIS In-Process Applications.” Any application can be moved in-process or out-of-process and started or stopped at will since it is hosted in an MTS package
All of the usual MTS services are available to the WAM, including connection pooling, distributed transaction processing, and creating the object context.
When an HTTP request comes into the server, processed, and the Web server determines whether it is plain HTML (or other plain MIME types) or a request for an ISAPI or ASP application. If it is ISAPI or ASP, the WAM map consulted, and the request routed to the appropriate WAM. As previously mentioned, WAMs can manage in-process or out-of-process applications.
