IBM z/OS manual Queued Direct Input/Output Qdio, Z990 OSA-Express Gigabit Ethernet

Queued Direct Input/Output (QDIO)

The OSA-Express Gigabit Ethernet, 1000BASE-T Ethernet and Token-Ring features support QDIO (CHPID type OSD), which is unique to IBM. QDIO was fi rst introduced to the world on the z900, in Communication Server for OS/390 2.7.

Queued Direct Input/Output (QDIO), a highly effi cient data transfer architecture, breaks the barriers associated with the Channel Control Word (CCW) architecture increasing data rates and reducing CPU cycle consumption. QDIO allows an OSA-Express feature to directly communicate with the server’s communications program through the use of data queues in memory. QDIO helps eliminate the use of channel program and channel control words (CCWs), helping to reduce host interrupts and accelerate TCP/IP packet transmission.

TCP/IP connectivity is increased with the capability to allow up to a maximum of 160 IP stacks per OSA-Express port and 480 devices. This support is applicable to all the OSA-Express features available on the z990 and is pro- vided through the Licensed Code (LIC).

Full Virtual Local Area Network (VLAN) support is available on z990 in z/OS V1.5 Communications Server (CS) for the OSA-Express 1000BASE-T Ethernet, Fast Ethernet and Gigabit Ethernet features when confi gured in QDIO mode. Full VLAN is also available with z/OS V1.2 on z900 and z800 using appropriate LIC upgrade on Fast Ethernet and Gigabit Ethernet features. Full VLAN support in a Linux on zSeries environment was delivered for QDIO mode in April 2002 for z800 and z900. z/VM V4.4, and later, also exploits the VLAN technology offering one global VLAN ID for IPv4. z/VM V5.1 provides the support for one global VLAN ID for IPv6.

z990 OSA-Express Gigabit Ethernet

The new z990 OSA-Express Gigabit Ethernet LX and Giga- bit Ethernet SX features replace the z900 Gigabit Ethernet features for new build z990. The new OSA-Express GbE features have a new connector type, LC Duplex, replacing the current SC Duplex connectors used on the prior z900 Gigabit Ethernet features. The new Checksum offl oad sup- port on these z990 features is designed to offl oad z/OS V1.5 and Linux on zSeries TCP/IP stack processing of Checksum packet headers for TCP/IP and UDP.

QDIO Mode - TCP/IP

pSeries, RS/6000

Gigabit Ethernet (fiber or copper)

xSeries, Netfinity

4/16/100 Mbps

Gigabit Ethernet Token-Ring

Switch / (fiber or copper) Router

Gigabit		Server
Ethernet
	10/100 Mbps	IP
		Router
Server	Ethernet
	Server
	IP WAN	Internet or
	Intranet	extranet

TCP/IP applications	Remote Office
TN3270 browser	IP Router
access to SNA appls.
Enterprise Extender
for SNA end points

	10/100 Mbps
4/16 Mbps	Ethernet
Token-Ring
	Server

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