The reliability, availability, and serviceability goal for an IBM zSeries® system is to provide 24-hour-per-day, 365-day-per-year service with reduced system downtime. The continuous reliable operation rate has been improved with every new zSeries release by using error prevention, error detection, error recovery, and other methods that contribute to avoiding unplanned interruptions. Until now, planned downtime—for example, the time needed to upgrade a zSeries to the next firmware driver—had not yet been addressed. We developed the concurrent driver upgrade (CDU) feature so that customers could add new functions without downtime. It is now possible to upgrade the zSeries firmware engineering change (EC) driver to the next EC level without any performance impact during the upgrade. This paper describes the motivation and strategy of the CDU and describes its use.
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