The IBM System z® mainframe computer is a direct descendant of the IBM System/360 family of computing systems initially made available in 1965. With each release of an IBM mainframe, its developers include new reliability, availability, and serviceability (RAS) functions. This paper describes recent technology added to the System z and z/OS® operating system to enhance the ability to provide high levels of availability. Specifically, we discuss the use of machine-learning algorithms to analyze log messages. We also describe combining temporal and textual information for system log-file analysis. Finally, we discuss the results of this analysis and the assistance it provides to mainframe users. © 1957-2012 IBM.