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Getting the Most Out of OSA and HiperSockets with z/OS Communications Server

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With enterprise server platform workloads relying heavily on network communications, companies are looking for a way to handle those workloads reliably and securely. IBM Master Inventor Jerry Stevens outlined in his SHARE Pittsburgh Best of the Best winning session, Getting the Most Out of OSA and HiperSockets with z/OS Communications Server, how enterprises could achieve those goals.

“System Z, z/OS communications server, OSA-Express, and HiperSockets combine to provide cutting edge network technology for our z/OS customers,” he said. “z/OS network system administrators have a lot to think about, from security and network bandwidth to provisioning, sharing, response time, high availability, and monitoring, among other things. We want to make sure our users can navigate the maze of deployment and usage considerations.”

The z/OS communications server uses OSA for IPv4/IPv6 LAN connectivity based on Queued Direct IO (QDIO) architecture by communicating with and managing OSA to provide unique services. This allows an operating system to exploit OSA in "layer 3" (L3) mode or in "layer 2" (L2) mode, says Stevens. In L3 mode, OSA is aware of the layer 3 protocol (IP) and provides various IP assists to displace processing from z/OS to OSA. Additionally, the host registers IP addresses that are owned by that operating system. In L2 mode, OSA routes inbound traffic based on MAC addresses and is not aware of the layer 3 protocol. z/OS uses L3 mode only for OSA.

HiperSockets also uses the QDIO architecture. This architecture provides advantages in unique network processing, allowing software, firmware, and hardware to work together to provide unique industry-leading z/OS features, Stevens adds. These include the QDIO accelerator, HSCI, IWQ, and WLM priority queuing, assuring that z/OS clients continue to meet their business objectives.

Two Key Optional Configurations for OSA Features

For outbound network traffic, IBM recommends that users prioritize the OSA processing of outbound traffic. Firms can do this by enabling a feature called "OSA WLM PRIORITY Queuing," Stevens says. “With just one setting on the TCP/IP GlobalConfig statement called “WLMPRIORITYQ,” he says, “the communications server will map the WLM importance level of the application workload to one of four outbound transmit queues. This allows OSA to process (transmit) work based on the natural job priority (defined by the user in WLM) of each application workload.”

For inbound network traffic, IBM recommends that users enable a feature called “Inbound Workload Queueing” (enabled in the OSA INTERFACE statement with INBPERF=WORKLOADQ), which causes OSA to separate traffic off the wire onto unique inbound work queues. Stevens explains, “This allows the software to provision the appropriate resources for optimizing the unique processing required for each input queue for workloads, such as streaming, Sysplex Distributor or QDIO accelerator, Enterprise Extender, IPSec, or zCX. IPSec and zCX workloads are zIIP eligible.”

Stevens notes that users need to understand how z/OS interacts with OSA and HiperSockets using the QDIO architecture and what options are available to provide better control and management of network traffic. These options also can provide them with a better way to monitor activity, he said.

Ultimately, enterprises need to choose the best OSA configuration and features for their workloads and environment to maximize the benefits of the technology. Some of those benefits can include CPU savings, better response times, higher availability, and operational and bandwidth improvements.

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