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IBM mainframe	Architecture
700/7000 series	varied
System/360
System/370	System/370
	S/370-XA
	ESA/370
System/390	ESA/390
zSeries	z/Architecture
System z9
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IBM System z, or earlier IBM eServer zSeries, is a brand name designated by IBM to all its mainframe computers.

In 2000, IBM rebranded 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 one generation of mainframes, starting with z900.

Since April 2006, with another generation of products, the official designation has changed to IBM System z, which now includes both^[1] older IBM eServer zSeries and newer IBM System z9 models.

The zSeries line succeeded the System/390 line (S/390 for short), maintaining full backward compatibility. In effect, zSeries machines are the direct, lineal descendants of System/360, announced in 1964, and the System/370 from 1970s . Applications written for these systems can still run, unmodified, with only few exceptions, on the newest System z over four decades later.

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

The z900 was a powerful machine, compared to its predecessors, a machine which introduced 64-bit computing into the mainframe world using the newly-designed z/Architecture. The new servers provided more than twice the performance of previous models. In its 64-bit mode the new CPU became free from the 31-bit addressing limits of its predecessors.

Major features of the eServer zSeries family:

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

In July 2005, IBM announced a new brand name System z9 using it to announce the latest generation System z9-109 servers.

The System z9 servers add on top of that:

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

The System z9-109 Model S54, with up to 54 processing units (PUs), 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 configured, or "characterized", for a variety of purposes including general purpose processing (CPs), zAAPs, zIIPs, IFLs, and ICFs.

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.

The older S/390 IBM mainframe servers are considered history since support for the last S/390 compatible version of z/OS (1.5) was dropped on March 31, 2007.^[2]

zSeries mainframes:

• z900 (2064 series), 2000,
• z800 (2066 series), entry-level, less powerful variant of the z900
• z990 (2084 series), successor to larger z900 models
• z890 (2086 series), 2004, successor to the z800 and smaller z900 models

System z9 mainframes:

• z9 Enterprise Class (2094 series), introduced in 2005 initially as z9-109, the new System z9 line
• z9 Business Class (2096 series), 2006, successor to z890

Future

• Undisclosed systems using z6 processors in 2007/2008.

• List of IBM products
• Linux on zSeries
• zAAP
• zIIP
• Peer to Peer Remote Copy
• Extended Remote Copy
• LPAR
• HiperSocket
• ESCON
• FICON
• Sysplex
  • Parallel Sysplex
  • Geographically Dispersed Parallel Sysplex
• Hercules emulator

• IBM: zSeries/z9 Mainframes
• IBM: System z9 109
• IBM: zSeries Timeline
• Z6 microprocessor The follow-on to Z9, by Charles F. Webb of IBM