Draft Document for Review April 7, 2004 6:15 pm

6947ch02.fm

Optionally assignable SAPs

Assigned CPs may be optionally reassigned as SAPs instead of CPs, using the Reset Profile on the Hardware Management Console (HMC). This reassignment increases the capacity of the Channel Subsystem to perform I/O operations, usually for some specific workloads or I/O intensive testing environments.

if you intend to activate a modified server configuration with a modified SAP configuration, a reduction in the number of CPs available will reduce the number of logical processors you can activate. Activation of a logical partition will fail if the number of logical processors you attempt to activate exceeds the number of CPs available. To avoid a logical partition activation failure, you should verify that the number of logical processors assigned to a logical partition does not exceed the number of CPs available.

Note: Concurrent upgrades are not supported with CPs defined as additional SAPs.

Reserved processors

Reserved processors can be defined to a logical partition. Reserved processors are defined by the Processor Resource/System Manager (PR/SM) to allow non-disruptive capacity upgrade. Reserved processors are like “sparelogical processors.” They can be defined as

Shared or Dedicated.

Reserved processors can be dynamically configured online by an operating system that supports this function if there are enough unassigned PUs available to satisfy this request. The previous PR/SM rules regarding logical processor activation remain unchanged.

Reserved processors also provide the capability of defining to a logical partition more logical processors than the number of available CPs, IFLs, ICFs, and zAAPs in the configuration. This makes it possible to configure online, non-disruptively, more logical processors after additional CPs, IFLs, ICFs, and zAAPs have been made available concurrently, via CUoD, CIU, and On/Off CoD for CPs, IFLs, ICFs, and zAAPs, or CBU for CPs. See “Concurrent upgrades” on page 186 for more details.

When no reserved processors are defined to a logical partition, a processor upgrade in that logical partition is disruptive, requiring the following tasks:

1.Partition deactivation

2.A Logical Processor definition change

3.Partition activation

The maximum number of Reserved processors that can be defined to a logical partition depends upon the number of logical processors that are defined. For an ESA/390 mode logical partition the sum of defined and reserved logical processors is limited to 32, including CPs and zAAPs. However up to 24 processors, including CPs and zAAPs, are planned to be supported by z/OS 1.6. The z/VM 5.1 is planned to support up to 24 processors, either all CPs or all IFLs.

For more information about logical processors and reserved processors definition, see “Logical Partitioning overview” on page 57.

Processor unit characterization

Processor unit (PU) characterization is done at Power-on Reset time when the server is initialized. The z990 is always initialized in LPAR mode, and it is the PR/SM hypervisor that has responsibility for the PU assignment.

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IBM 990 manual Reserved processors, Processor unit characterization, Optionally assignable SAPs
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990 specifications

The IBM 990 series, often referred to in the context of IBM's pioneering efforts in the realm of mainframe computing, represents a unique chapter in the history of information technology. Introduced in the late 1960s, the IBM 990 series was designed as a powerful tool for enterprise-level data processing and scientific calculations, showcasing the company's commitment to advancing computing capabilities.

One of the main features of the IBM 990 was its architecture, which was built to support a wide range of applications, from business processing to complex scientific computations. The system employed a 32-bit word length, which was advanced for its time, allowing for more flexible and efficient data handling. CPUs in the IBM 990 series supported multiple instructions per cycle, which contributed significantly to the overall efficiency and processing power of the machines.

The technology behind the IBM 990 was also notable for its use of solid-state technology. This provided a shift away from vacuum tube systems that were prevalent in earlier computing systems, enhancing the reliability and longevity of the hardware. The IBM 990 series utilized core memory, which was faster and more reliable than the magnetic drum memory systems that had been standard up to that point.

Another defining characteristic of the IBM 990 was its extensibility. Organizations could configure the machine to suit their specific needs by adding memory, storage, and peripheral devices as required. This modular approach facilitated the growth of systems alongside the technological and operational demands of the business environments they served.

In terms of software, the IBM 990 series was compatible with a variety of operating systems and programming environments, including FORTRAN and COBOL, enabling users to access a broader array of applications. This versatility was a significant advantage, making the IBM 990 an appealing choice for educational institutions, research facilities, and enterprises alike.

Moreover, the IBM 990 was engineered to support multiprocessing, which allowed multiple processes to run simultaneously, further increasing its effectiveness in tackling complex computing tasks.

In summary, the IBM 990 series represents a significant advancement in computing technology during the late 20th century. With a robust architecture, versatile configuration options, and a focus on solid-state technology, the IBM 990 facilitated substantial improvements in data processing capabilities, making it a cornerstone for many businesses and academic institutions of its time. Its impact can still be seen today in the continued evolution of mainframe computing.
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