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

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Figure 2-16 Logical processor assignment (HMC- Image Profile)

On the z990, the sum of defined and reserved logical processors for an ESA/390 mode logical partition is limited to 32. However, z/OS 1.6 and z/VM 5.1 operating systems are planned to support up to 24 processors. For z/OS, the 24 processors limit applies to the sum of CPs and zAAPs logical processors. The weight and the number of online logical processors of a logical partition can be dynamically managed by the LPAR CPU Management function of the Intelligent Resource Director, to achieve the defined goals of this specific partition and of the overall system.

￿Memory

Memory, either Central Storage or Expanded Storage, must be dedicated to a logical partition. The defined storage(s) must be available during the logical partition activation; otherwise, the activation fails.

Reserved storage can be defined to a logical partition, enabling non-disruptive memory add to and removal from a logical partition, using the LPAR Dynamic Storage Reconfiguration. Refer to “LPAR Dynamic Storage Reconfiguration (DSR)” on page 71 for more information.

￿Channels

Channels can be shared between logical partitions by including the partition name in the partition list of a Channel Path ID (CHPID). I/O configurations are defined by the I/O Configuration Program (IOCP) or the Hardware Configuration Dialog (HCD) in conjunction with the CHPID Mapping Tool (CMT). The CMT is an optional, but strongly recommended, tool used to map CHPIDs onto Physical Channel IDs (PCHIDs) that represent the physical location of a port on a card in an I/O cage.

Chapter 2. System structure and design 59

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IBM 990 manual Memory, Channels
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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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