IBM Midrange is a general term referring to the business computing platform also known as AS/400, iSeries, i5, IBM i, et al.
Originally introduced on June 21, 1988 the platform has been continually updated to support and integrate with modern technologies while maintaining source and binary compatibility.
The platform includes an integrated db2 database server and natively supports many application servers including websphere, apache httpd and tomcat.
Common programming languages for the IBM Midrange platform include:
For more information see the Wikipedia article on IBM System i.