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

6947ch07.fm

Link Type

z990 Max

 

 

Maximum number of links per z990

64b

a. A maximum of 32 ISC-3s can be defined in compatibility mode, which operates at to 1 Gb/s.

b. The maximum number of external and internal Coupling Links combined (ICB-2, ICB-3, ICB-4, ISC-3, and active IC links) cannot exceed 64 per system.

Refer to Table 7-3for an overview of the CF link connectivity options for the various supported servers.

Table 7-3 z990 CF link connectivity

Connectivity

z990 ISC-3

z990 ICB-2

z990 ICB-3

z990 ICB-4

options

 

 

 

 

 

 

 

 

 

G5/G6 ISC

1 Gbit/sec

N/A

N/A

N/A

 

Compat Mode

 

 

 

 

 

 

 

 

z800/z900 ISC-3

2 Gbit/sec

N/A

N/A

N/A

 

Peer Modea

 

 

 

z890/z990 ISC-3

2 Gbit/sec

N/A

N/A

N/A

 

Peer Modea

 

 

 

G5/G6 ICB

N/A

333 MBytes/sec

N/A

N/A

 

 

Compat Mode

 

 

 

 

 

 

 

z900 ICB-2

N/A

Not supported

N/A

N/A

 

 

 

 

 

z990 ICB-2

N/A

Not supported

N/A

N/A

 

 

 

 

 

z900 ICB-3

N/A

N/A

1 GByte/sec

N/A

 

 

 

Peer Mode

 

 

 

 

 

 

z990/z890 ICB-3

N/A

N/A

1 GByte/sec, Peer

N/A

 

 

 

mode,

 

 

 

 

Recommendation

 

 

 

 

use ICB-4

 

 

 

 

 

 

z990/z890 ICB-4

N/A

N/A

N/A

2GBytes/sec

 

 

 

 

Peer Mode

 

 

 

 

 

a. 1 Gbit/sec when 20km RPQ 8P2197 is installed.

Peer mode links

There are several advantages in using peer mode links; first of all peer mode links operate on a higher bandwidth than the equivalent Compatibility mode link. A single CHPID (one side of the link) can be both sender and receiver; this means that a single CHPID can be shared between multiple OS logical partitions and one Coupling Link logical partition. The number of link buffers provided when peer mode links are used is seven (7) per link compared to 2 per link in Compatibility mode; this is particularly important with System-Managed CF Structure Duplexing. Peer links have 224 KB data buffer space compared to 8 KB on Compatibility mode links; this is especially important for long distances as it reduces the handshaking for large data transfers.

z/OS and/or OS/390 images and Coupling Facility images may be running on the same or on separate servers. Every z/OS or OS/390 image in a Parallel Sysplex must have at least one coupling link to each CF image.

Chapter 7. Sysplex functions 163

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Image 177
IBM manual Peer mode links, Link Type Z990 Max Maximum number of links per z990

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.