"Good things come in small packages."  This is certainly true for IBM’s System z OSA-Express device, which is a powerful network control unit about the size of a paperback novel.  Here are 5 things to know about OSA-Express features:
 

1. OSA-Express devices access the internet as well as intranets.

OSA devices are designed for high-speed communication in the mainframe enterprise backbone or between campuses, to connect server farms, or to consolidate file servers onto an IBM zEnterprise System. The workload can be Internet Protocol (IP) based or non-IP based. OSA-Express5S is an integrated hardware feature optimized for mainframe Ethernet local area network (LAN) connectivity.

2. Direct Memory Access speeds processing.

The OSA-Express devices share a common storage area for memory-to-memory communication, reducing system overhead and improving performance. The System z is known for its ability to be a server to hundreds or thousands of user devices.
 

3. Hardware data router improves performance.

With OSA-Express devices, much of what was previously done in firmware, such as packet construction, inspection, and routing, is now performed in hardware. This allows packets to flow directly from host memory to the LAN without firmware intervention. With the hardware data router, the store-and-forward technique is no longer used.  This enables true direct memory access to the LAN, which optimizes the OSA processing.  This improves both latency and throughput, thereby improving application performance.

4. Dynamic reconfiguration reduces outages.

Dynamic reconfiguration management is the ability to select a new I/O configuration during normal processing, without the need to perform a power-on reset (POR) of the hardware or an IPL of the z/OS operating system. The ability of HCD to provide equivalent hardware and software I/O definitions and to detect when they are not in sync is essential for dynamic I/O reconfiguration management. HCD compares both the old and the new configuration and informs the hardware and software about the differences. You may add, delete, and modify definitions for channel paths, control units and I/O devices (including OSA) without having to perform a POR or an IPL.
 

5. OSA/SF provides support for operational and administrative tasks.

The Open Systems Adapter Support Facility (OSA/SF) is an application that helps you to customize and manage your OSA features. It also allows you to obtain status and operational information about the HCD-defined OSA ports to assist in problem determination.  While previous OSA devices were supported by OSA/SF on the operating system, the latest device (OSA-Express5S) is supported by OSA/SF on the hardware management console (HMC) as shown in the figure below.

OSA devices are supported by the mainframe operating systems:  z/OS, z/VM, z/VSE, z/TPF and Linux on System z. For more information, read OSA-Express Implementation Guide, SG24-5948.

Mike Ebbers is an IBM Redbooks Project Leader. He works with technical experts to create books, guides, blogs, and videos. Follow Mike on Twitter at @MikeEbbers.