1. TP Monitors: TP monitors stands for Transaction Processing Monitor. It was
possibly the first product to be called middleware. TP monitor is the extra
layer between the client program and the servers. It ensured that all databases
are updated properly in a single transaction. Examples of popular TP monitors
are CICS, a veteran TP monitor used on IBM mainframes and the Unix-based Tuxedo
and Encina products.
2. Application Server Middleware A Web-based application server that provides interfaces to a wide variety of applications is used as middleware between the browser and legacy systems. The browser can be used on desktops or laptops even when traveling. A wide range of server-side processing has been supported by appservers. An example is JAVA EE. Please watch the following video as it is a perfect example of application server middleware.
3. Database Middleware: Database middleware is any middleware that helps communications with a database either from an application or by databases. Developers typically use database middleware as a tool to take out information, whether from local or remote databases. An example of a popular database middleware is Oracle database.