Sunday, 7 March 2010

What's going on - on my Open Systems Adapter?

An Open Systems Adapter (OSA) is a network controller between mainframes and other computing platforms. An OSA supports Ethernet, Token Ring, and FDDI (Fibre Distributed Data Interface) connectivity, and can offer data throughput speeds of up to 10 gigabits per second. An OSA provides a way of attaching a LAN (Local Area Network) to a mainframe, or looking at it the other way round, it provides a way of connecting a mainframe to a LAN! Either way, it makes it a very crucial piece of kit.

At most installations, life isn't quite so simplistic. For example, a single OSA can be shared across several LPARs and/or IP stacks. It can handle multiple channels and multiple types and instances of ports. And the consequence of this is its ability to support a very large number of users.

You'd think this kind of complexity would make the OSA a device that is monitored by every site that's got one. After all, what would happen were it to suddenly stop working? But the complexity doesn't stop there. An OSA exists as a z/OS device, a VTAM device, an IP interface, and an SNMP device. And it's this level of complexity that makes the collection of data so tricky. There's not even some low-level tool providing a single query that will reveal how an OSA is performing.

In truth, OSAs are resilient, managing to recover and log any non-fatal errors encountered in an internal Management Information Base (MIB). The MIB is a database containing information about the current OSA set-up and state information. Getting information out of the MIB is only possible with low-level tools and a good knowledge of the associated MIB structures. An OSA MIB may well contain many thousands of separate fields identified by Object Id and an Index relating them to a specific LPAR, channel, or port. Additional information about an OSA can be found in z/OS device tables, IP stacks, and VTAM control blocks.

Perhaps surprisingly, many sites feel that an IP monitor is probably all that's needed to keep an eye on their OSA. However, a new alternative is ZEN OSA Monitor (ZOM) from William Data Systems ( ZOM provides users with the ability to get a health check of their OSA, and it also provides a soft reset feature. According to the WDS Web site: "ZOM dynamically detects any status changes or increases in error counts, with all such changes summarized in easy-to-read panels in ZEN, with full alerting and reporting capabilities. A simple but effective system of traffic lights highlight any changes to reference values, ensuring these critical devices are maintained at optimal performance levels."

Some readers may be familiar William Data Systems ZEN EE (Enterprise Extender) Monitor, codenamed Ferret.

With ZOM, the OSA dashboard provides an at-a-glance list of a user's monitored OSAs with an indication of current usage and status. Several fields contain drill-down links to further, more detailed displays.

With OSA devices playing such a critical role in the communication between mainframes and the rest of the computing environment, it would make sense to utilize a product that's able to access important performance data and display it in an easily digestible format. Anyway, they're not paying me to sell their product for them, but I thought readers of this blog would find the existence of this software well worth knowing about.

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