In this appendix
Contributed by Wolfgang Gellerich, IBM
Fortunately, there are rather few specific issues to be considered when porting application programs to Linux running on an IBM zSeries mainframe, because the "official" interfaces of the Linux kernel are platform-independent. One important difference, however, concerns the way the Linux system itself executes on a mainframe. Personal computers usually run a native operating system controlling the whole computer system. In contrast, IBM zSeries systems support the concept of virtualization. Any operating system within the zSeries platform executes in a virtual environment, and there may be (and normally are) several instances of several different operating systems running at the same time.