This post is part of a series exploring the unique aspects and capabilities of WebSphere Liberty when running on z/OS.
We'll also explore considerations when moving from WebSphere traditional on z/OS to Liberty on z/OS.
The next post in the series is here.
To start at the beginning, follow this link to the first post.
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For any pricing model based on actual usage of a product there has to be some mechanism to track how much that product gets used. On z/OS this is done via a report produced by the SCRT tool (which is redundant because the ‘T’ in SCRT is ‘tool’). The SCRT report is generated from SMF records produced by z/OS itself. Those SMF records report usage of the system by particular products.
Ok, so how does z/OS know which product is running in which address space? In general it is because something running in that address space has called the IFAUSAGE API. This service allows a product to identify itself to z/OS. There are a bunch of parameters, but the key one is the product ID (PID). There are also other ways to register, but this is how Liberty does it.
It is possible for more than one product to register its presence in the same address space. You might get that if an IBM software product is running inside a customer-purchased WebSphere server (instead of including WAS with the product). That doesn’t happen very much, but when it does you’ll have both products present in that one address space and CPU usage is attributed to both.
The most common scenario is, of course, a customer application running inside WebSphere in which case the server registers using the WAS PID and that’s that. But there are quite a few IBM products that rely on a copy of WAS Liberty either embedded inside that product, or use the one embedded in z/OS (that we discussed a couple of weeks back).
In this case, WAS doesn’t register as itself at all, but instead just as whatever the exploiting product is. That’s how z/OSMF and z/OS Connect register. They provide configuration that tells Liberty to register using their PID instead of the WebSphere PID. CICS does the same thing, even though CICS isn’t running inside Liberty, but more the other way ‘round.
But what if you start the Liberty Embedded in z/OS, but just to try it out and not as part of an exploiting IBM product? Well, starting with some changes shipped in late 2021, Liberty Embedded will register as a special PID that indicates it is this special copy of Liberty. Your usage of it will show up in the SCRT report, but such usage is allowed (as discussed earlier, for “non-production purposes”) and won’t raise any flags.
So now you can look at your SCRT report and see what it is telling you (and IBM) about your usage of WAS z/OS.