| IBM mainframe | Architecture |
| 700/7000 series | varied |
| System/360 | unified |
| System/370 | System/370 |
| S/370-XA | |
| ESA/370 | |
| System/390 | ESA/390 (ARCHLVL 1) |
| zSeries | z/Architecture 1 (ARCHLVL 2) |
| System z9 | |
| System z10 | z/Architecture 2 (ARCHLVL 3) |
| zEnterprise z196 | |
| zEnterprise z114 | |
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, the IBM System z9 models, the IBM System z10 models, and the newer IBM zEnterprise.
Both zSeries and System z brands are named for their availability — z stands for zero downtime. The systems are built with spare components capable of hot failovers to ensure continuous operations.[2]
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.
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The z900 was a powerful machine (compared to its predecessors), a machine which introduced IBM's newly-designed z/Architecture into the 64-bit mainframe world. 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:
In July 2005, IBM announced a new brand name System z9 using it to announce System z9-109 servers.
The System z9 servers add on top of that:
The System z9-109 Model S54, with up to 54 processing units (PUs), is 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.
The IBM System z10 servers have many similarities to z9 servers but support more memory and can have up to 64 central processors (CPs) per frame. The full speed z10 processor's uniprocessor performance is up to 62% faster than that of the z9 server, according to IBM's z10 announcement.
The IBM zEnterprise System, or z196, introduced in July, 2010, supports up to 80 central processors of up to 5.2GHz, and 3TB of memory. The zEnterprise also supports x86 or Power blades attached as a zEnterprise BladeCenter Extension (zBX).
A direct comparison of System z servers with other computing platforms is difficult. For example, System z servers offload such functions as I/O processing, cryptography, memory control, and various service functions (such as hardware configuration management and error logging) to dedicated processors. These "extra" processors are in addition to the (up to) 80 main CPs per frame. System z cores include extensive self checking of results, and if an error is detected the server retries the instruction. If the instruction still fails, the server shuts down the failing processor and shifts workload, "in flight," to a surviving spare processor. The IBM mainframe then "calls home" (automatically places a service call to IBM). An IBM service technician replaces the failed component 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 can extend to coupled frames separated by up to 100 kilometers in a Geographically Dispersed Parallel Sysplex when z/OS is used.
System z 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, System z machines may 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 System z 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.[3]
zSeries mainframes:
System z9 mainframes:
System z10 mainframe:
zEnterprise System mainframe: