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

6947ch01.fm

1.3.5 Physical Channel IDs (PCHIDs) and CHPID Mapping Tool

A z990 can have up to 1024 physical channels, or PCHIDs. In order for an operating system to make use of that PCHID, it must be mapped to a CHPID within the IOCDs. Each CHPID is uniquely defined with an LCSS and mapped to an installed PCHID. A PCHID is eligible for mapping to any CHPID in any LCSS.

The z990 CHPID Mapping Tool (CMT) provides a method of customizing the CHPID assignments for a z990 system to avoid attaching critical channel paths to single points of failure. It should be used after the machine order is placed and before the system is delivered for installation. The tool can also be used to remap CHPIDs after hardware upgrades that increase the number of channels.

The tool maps the CHPIDs from an IOCP file to Physical Channel Identifiers (PCHIDs) which are assigned to the I/O ports. The PCHID assignments are fixed and cannot be changed.

A list of PCHID assignments for each hardware configuration is provided in the PCHID Report available when z990 hardware is ordered. Unlike previous zSeries systems, there are no default CHPID assignments. CHPIDs are assigned when the IOCP file is built. When upgrading an existing zSeries configuration to z990, CHPIDs can be mapped by importing the IOCP file into the z990 CHPID Mapping Tool.

1.3.6 Spanned channels

As part of the z990 LCSS, the Channel Subsystem is extended to provide the high-speed, transparent sharing of some channel types in a manner that extends the MIF shared channel function. Internal Channel types such as HiperSocket (IQD) and Internal Coupling Channels (ICP) can be configured as “spanned” channels. External channels such as FICON channels, OSA features, and External Coupling Links can be defined as spanned channels. Spanned channels will allow the channel to be configured to multiple LCSSs, thus enabling them to be shared by any/all of the configured logical partitions, regardless of the LCSS in which the partition is configured.

Note: Spanned channels are not supported for ESCON channels, FICON conversion channels (FCV), and Coupling Receiver links (CBR, CFR).

Chapter 1. IBM zSeries 990 overview 7

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IBM 990 manual Physical Channel IDs PCHIDs and Chpid Mapping Tool, Spanned 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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