Parallel Sysplex Connectivity; Coupling Links - IBM z13s Technical Manual

Shared Memory Communication - Direct Memory Access
With the z13 and z13s servers, IBM introduces Shared Memory Communication - Direct
Memory Access (SMC-D). SMC-D maintains the socket-API transparency aspect of SMC-R
so that applications using TCP/IP communications can benefit immediately without requiring
any application software or IP topology changes. SMC-D completes the overall Shared
Memory Communications solution, providing synergy with SMC-R. Both protocols use shared
memory architectural concepts, eliminating TCP processing in the data path, yet preserving
TCP/IP Qualities of Service for connection management purposes.
Internal Shared Memory
Internal Shared Memory (ISM) is a new function supported by the z13 and z13s machines. It
is the firmware that provides the connectivity for shared memory access between multiple
operating systems within the same CPC. ISM creates virtual adapters with shared memory
allocated for each OS, that OS can use these virtual adapters for SMC-D data exchanges
within the same CPC.
ISM is defined by FUNCTION statement with a VCHID in HCD/IOCDS. Identified by the
PNETID parameter, each ISM VCHID defines an isolated, internal virtual network for SMC-D
communication, without any hardware component required. Virtual adapters are defined by
virtual function (VF) statements. Multiple LPARs have share accessing to same virtual
network for SMC-D data exchange by associating their VF with same VCHID.
z13s servers support up to 32 ISM VCHIDs per CPC, and each VCHID supports up to 255
VFs, with a total maximum of 8K VFs. For more information about the SMC-D and ISM, see
Appendix D, "Shared Memory Communications" on page 475
HiperSockets can have network latency and CPU reduction benefits and performance
improvement, by using the SMC-D over ISM.

4.9 Parallel Sysplex connectivity

Coupling links are required in a Parallel Sysplex configuration to provide connectivity from the
z/OS images to the coupling facility. A properly configured Parallel Sysplex provides a highly
reliable, redundant, and robust z Systems technology solution to achieve near-continuous
availability. A Parallel Sysplex is composed of one or more z/OS operating system images
that are coupled through one or more coupling facilities.

4.9.1 Coupling links

The type of coupling link that is used to connect a coupling facility (CF) to an operating
system LPAR is important. The link performance has a significant effect on response times
and coupling processor usage. For configurations that cover large distances, the time that is
spent on the link can be the largest part of the response time.
These links are available to connect an operating system LPAR to a coupling facility:
Integrated Coupling Adapter (ICA SR) for short distance connectivity and defined as
CHPID type CS5. The ICA SR can be used only for coupling connectivity between z13 and
z13s servers. It does not support connectivity to zEC12, zBC12, z196, or z114 servers,
and it cannot be connected to HCA3-O or HCA3-O LR coupling fanouts. The ICA SR
supports distances up to 150 m and a link data rate of 8 GBps. OM3 fiber optic cable is
used for distances up to 100 m, and OM4 for distances up to 150 m. ICA SR supports four
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IBM z13s Technical Guide