System z InfiniBand Redbook updated
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InfiniBand coupling links were a huge step forward for System z coupling. For the first time, a single physical coupling link could be shared across more than one sysplex. They provide the flexibility to assign multiple CHPIDs to a single coupling link. The 1X links provide the ability to have up to 32 subchannels per CHPID, thereby addressing the high subchannel utilization that is common when using a sysplex that spans multiple sites. And the 12X links, when run in IFB3 mode, deliver significantly better response times than the original 12X links and the older ICB4 links. All of these enhancements, and more, are documented in the Redbook, Implementing and Managing InfiniBand Coupling Links on System z, SG24-7539, that we released in March 2012.
If there was a downside to the InfiniBand links, it was the fact that, to fully understand the InfiniBand infrastructure, you had to use a combination of the D CF command, and the Support Element. But this has been addressed on zEC12 and zBC12, which provide a wealth of information about the InfiniBand infrastructure to z/OS. And that information, in turn, can be displayed using the D CF MVS command, and also in RMF.
Previously, there was no way to determine from the D CF command what type of link was being used, of if there were any single points of failure in the configuration. But if z/OS is running on a zBC12 or zEC12, the output now contains this:
PATH PHYSICAL LOGICAL CHANNEL TYPE AID PORT B1 / 0723 ONLINE ONLINE CIB 12X-IFB3 000A 02 B5 / 0724 ONLINE ONLINE CIB 12X-IFB3 001A 02 BA / 0727 ONLINE ONLINE CIB 1X-IFB 001D 01 BB / 0728 ONLINE ONLINE CIB 1X-IFB 001D 02
You can see that not only does the output show the link type, speed, and mode, it also shows the Adapter ID and Port, immediately letting you verify that there are no single points of failure.
Also, this information, and more, is available in RMF, both in realtime using Monitor III, and in the RMF CF Postprocessor report.
For more information on all these enhancements, and how they make it easier to manage a coupling configuration on a zEC12, see the latest edition of the Redbook, currently available as a draft on http
Please let us know if you find this new information helpful, or if you have any other suggestions about how the book could be more valuable to you. Happy reading!