5 coupling facility links – IBM 990 User Manual
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zSeries 990 Technical Guide
This function does not apply to IPv6 packets. TCP/IP will continue to perform all checksum
processing for IPv6 packets. This function also does not apply to ICMP checksum processing.
TCP/IP will continue to perform processing for ICMP checksum.
Checksum offload is supported by the OSA-Express GbE features (FC 1364, FC 1365) and
the 1000BASE-T Ethernet feature (FC 1366) when operating at 1000 Mbps (1 Gbps). This is
applicable to the QDIO mode only (channel type OSD).
z/OS support for Checksum offload is planned to be available in z/OS V1.5.
For Linux for zSeries support, refer to the following Web site for further information:
z990 adapter interruptions enhancement for QDIO
The z990 servers, Linux for zSeries, and z/VM work together to provide performance
improvements by exploiting extensions to the Queued Direct Input/Output (QDIO)
architecture. Adapter interruptions, first added to z/Architecture with HiperSockets, provide an
efficient, high-performance technique for I/O interruptions to reduce path lengths and
overhead in both the host operating system and the adapter - OSA-Express when using the
OSD CHPID type.
In extending the use of adapter interruptions to OSD (QDIO) channels, the programming
overhead to process a traditional I/O interruption is reduced. This benefits OSA-Express
TCP/IP support in both Linux for zSeries and z/VM.
Adapter interruptions apply to all of the OSA-Express features available on z990, whether
offered as a new build or on an upgrade from z900 when in QDIO mode (CHPID type OSD).
HiperSockets function
The HiperSockets function, also known as internal Queued Direct Input/Output (iQDIO) or
internal QDIO, is an integrated function of the z990 server that provides users with
attachment to up to sixteen high-speed “virtual” Local Area Networks (LANs) with minimal
system and network overhead.
HiperSockets eliminates the need to utilize I/O subsystem operations and the need to
traverse an external network connection to communicate between logical partitions in the
same z990 server. HiperSockets offers significant value in server consolidation connecting
many virtual servers, and can be used instead of certain XCF link configurations in a Parallel
Sysplex.
HiperSockets are customizable to accommodate varying traffic sizes. Since HiperSockets
does not use an external network, it can free up system and network resources, eliminating
attachment costs while improving availability and performance.
3.4.5 Coupling Facility links
What follows are Coupling Facility links connectivity options in the Parallel Sysplex
environment. For more information about Parallel Sysplex connectivity, see 7.2.4, “Coupling
Facility link connectivity” on page 164.
z990 coupling link features
z990 supports the following coupling link features:
Inter-System Channel-3, ISC-3 (Peer and Compatibility modes), feature codes 0217,
0218, and 0219