IBM zSeries

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IBM mainframes
IBM 700/7000 series IBM System/360 IBM System/370 IBM ESA/390 IBM zSeries

An IBM z890 mainframe

IBM zSeries is a brand name of IBM which was designated to all IBM mainframes in 2000 with the e depicted in IBM's red trademarked symbol.

The IBM eServer zSeries line succeeded the IBM System/390 (S/390 for short) which were based on the ESA/390 architecture while ensuring full compatibility to it. Thus, zSeries servers are the direct, lineal descendants of the IBM System/360, announced in 1964, and the 1970s System/370. Applications written for the 24-bit-addressing/32-bit-data System/360 can still run, unmodified, on the newest System z9 over four decades later, with few exceptions. IBM did not give the previous servers of the same line (IBM S/390) new names, so the term zSeries now popularly refers only to IBM's first line of 64-bit mainframes, starting with the first model of the new 64-bit mainframes the IBM zSeries 900 or, for short, z900.

The term "zSeries" is still the most popular way to refer to all IBM mainframe servers, probably because the older S/390 IBM mainframe servers will be considered history once support for the last S/390 compatible version of z/OS (1.5) is dropped on March 31, 2007.^[1] In its 64-bit mode the new CPU became free from the legacy of the 31-bit addressing limits of its predecessors.

1 Features
2 Models (chronological order)
3 See also
4 References
5 External links

[edit] Features

The z900 was (compared to its predecessors) a very powerful machine which introduced 64-bit computing into the mainframe world using the newly-designed z/Architecture. At the same time, the new servers provided more than twice the performance of previous models. In July 2005, IBM rebranded the server line again, to System z, but again not renaming previous servers. At the same time IBM announced a new brand name (System z9) using it to announce the latest generation System z9-109 servers. (See System z9 for information on the successor models to zSeries.)

Major features of the eServer zSeries family:

Based on z/Architecture (64-bit real and virtual addresses)
Offers up to 32 central processors (CPs) per frame (rack) coupled in up to a 32-frame Sysplex — with each frame physically separated up to 100 kilometers
Supports the Linux, z/OS, z/VM, z/VSE, z/TPF, and MUSIC/SP operating systems
S/390 ESA (31-bit) applications are fully compatible with z/Architecture
Some models introduced multiple I/O channel subsystems (exceeding the previous 256 channel limit) and zAAPs

The System z9 servers add on top of that:

Up to 54 central processors (CPs) per frame (rack)
zIIP engines
MIDAW
Advanced Encryption Standard (AES) cryptography implemented in hardware

The System z9-109 Model S54, with up to 54 "characterizable" PUs (processors), is currently the most powerful IBM mainframe available, reportedly capable of performing approximately 18,660,000,000 core instructions per second. A single S54 can typically process one billion or more business transactions per day — double the throughput of its predecessor. The 54 PUs can be characterized (configured) for a variety of purposes including general purpose processing (CPs), zAAPs, zIIPs, IFLs, and ICFs (coupling facilities).

A direct comparison of zSeries servers with other computing platforms is difficult. For example, zSeries servers offload such functions as I/O processing, cryptography, memory control, and various service functions (such as accounting and logging) to dedicated processors. These "extra" processors are in addition to the (up to) 54 main CPs per frame. The zSeries servers also effectively execute every instruction twice in order to assure processing integrity. If the instruction results differ, the zSeries server retries the instruction. If the instruction still fails, the zSeries/z9 server will shut down the failing processor and shift workload, "in flight," to any surviving processors, including one or more spares. The IBM mainframe then "calls home" (automatically places a service call to IBM), and an IBM service technician soon arrives with a replacement part (possibly even a new processor book, consisting of a group of processors). With System z9 servers, the technician installs the new book and removes the old one without interruption to running applications. (Note that IBM mainframe processors have a reported 40 year MTBF.) Similar design redundancies exist in memory, I/O, power, cooling, and other subsystems. All these features exist at the hardware and microcode level, without special application programming. The same concepts extend to coupled frames separated by up to 100 kilometers in a Geographically Dispersed Parallel Sysplex.

zSeries servers are used by IBM customers for business-critical installations in medium and large organizations which need very high availability, where scheduled and unscheduled downtime costs are high, and at traditional mainframe shops such as banks and insurance companies which already have mainframe applications at the center of their business processes. For such organizations which have to consider a very high price for system failures and service outages, zSeries machines provide a lower total cost of ownership than other platforms, especially when running a variety of business-critical applications concurrently (so-called mixed workload). Overall, mainframes like the zSeries are mostly used in government, financial services, retail, and manufacturing industries.

[edit] Models (chronological order)

z900 (2064 series)
z800 (2066 series), "cheaper", entry-level, less powerful variant of the z900
z990 (2084 series), successor to larger z900 models
z890 (2086 series), successor to the z800 and smaller z900 models

The zSeries era began in the year 2000 with the z900 and continued through 2004 with the introduction of the z890. The IBM System z9 (2094 series) debuted in 2005. The successor to the z890 the System z9 Business Class system (2096 series) was announced in 2006 and the System z9 (2094 series) was renamed as the System z9 Enterprise Class system. The System z9 EC and BC line of mainframes are the successors to all zSeries (and prior) models.