13.4 Change management

Those in the computer business who are responsible for availability often see system behavior as: "If the system ran yesterday and no one made a change to it, that system will probably keep running today." Sometimes this same understanding of change gets expressed by: "If the system fails today, the probable cause of the failure is the latest change made to the system."

While change poses a threat to availability, it is critical for continued existence in business. It is, in fact, the acceleration of change that is the hallmark of business today and one of the key drivers for deploying a Linux-on-the-mainframe environment.

Change management in most IT organizations is typically handled by some of the most skilled persons on the staff: the system administrators. We cover this topic in more detail in Chapter 16, "System Administrator Tasks."

With Linux on the mainframe, you typically apply changes to more than one image at a given time. The scripting capability of automation tools, and especially of z/VM, is one of the ways that provides significant control for the orderly introduction of complex changes into a large number of active systems. The use of automation is important for managing change in the Linux-on-the-mainframe environment.