IBM System z (officially "IBM z Systems") is a family name used by
IBM for all of its
mainframe computers. In 2000, IBM renamed the existing
System/390 to
IBM eServer zSeries with the
e depicted in IBM's red trademarked symbol, but because no specific machine names were changed for System/390, the
zSeries in common use refers only to the z900 and z990 generations of mainframes. In April 2006, with another generation of products, the official family was changed to
IBM System z, which now includes both older
IBM eServer zSeries, the
IBM System z9 models, the
IBM System z10 models, and the newer
IBM zEnterprise. The
zSeries,
System z and
zEnterprise families were named for their availability –
z stands for
zero downtime. The systems are built with spare components capable of hot
failovers to ensure continuous operations. The System z family maintains full
backward compatibility. In effect, current systems are the direct, lineal descendants of
System/360, announced in 1964, and the
System/370 from the 1970s. Many applications written for these systems can still run unmodified on the newest System z over five decades later.