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

6947ch07.fm

z/OS

ICF

 

CF to CF link

connectivity required for System-managed CF structure duplexing

ICF

z/OS

 

z800/z900/z990/z890/G5/G6z800/z900/z990/z890/G5/G6

Figure 7-7 System-managed CF structure duplexing

Whenever possible, try to comply with the following recommendations:

￿Provide two or more physical CF-to-CF links (peer mode), or two or more physical CF-to-CF links in each direction (sender/receiver mode), between each pair of CFs participating in duplexing. The physical CF-to-CF links may be shared by a combination of z/OS-to-CF links and CF-to-CF links.

￿For redundancy, provide two or more z/OS-to-CF links from each system to each CF. Provide dedicated z/OS-to-CF links if possible. If z/OS-to-CF links are shared between z/OS partitions, the occurrence of path busy conditions should be limited to at most 10 to 20 percent of total requests. If path busy exceeds this guideline, either provide dedicated links, or provide additional shared links, to eliminate or reduce the contention for these link resources. Use peer links whenever possible.

￿You can provide either dedicated or shared z/OS CPs when using system-managed CF structure duplexing. Dedicated Coupling Facility CPs are highly recommended for system-managed CF structure duplexing.

￿Be prepared to provide additional z/OS CPU capacity when the workload’s CF operations become duplexed. Provide sufficient Coupling Facility CP resources so that Coupling Facility CP utilization remains below 50% in all CF images.

￿Provide “balanced” Coupling Facility CP capacity between duplexed pairs of CFs. Avoid significant imbalances such as one CF with shared CPs and the other CF with dedicated CPs, CFs with wildly disparate numbers of CPs, CFs of different machine types with very different raw processor speed, and so forth.

￿As z/OS-to-CF and CF-to-CF distances increase, monitor the Coupling Facility link subchannel and path-busy status. If more than 10% of all messages are being delayed on the CF link due to subchannel or path busy conditions, either migrate to peer mode links to increase the number of subchannels for each link, or configure an additional link.

￿In a GDPS/PPRC multi-site configuration, do not duplex CF structure data between coupling facilities located in different sites; rather, if desired, duplex the structures between two coupling facilities located at the same site. CF structure data is not preserved in GDPS site failover situations, regardless of duplexing.

A technical paper on system-managed CF structure duplexing is available at:

http://www-1.ibm.com/servers/eserver/zseries/library/techpapers/gm130103.html

Chapter 7. Sysplex functions 169

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IBM manual Z800/z900/z990/z890/G5/G6z800/z900/z990/z890/G5/G6
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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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