Sometimes figuring out what's going on inside the IBM mainframe's specialty processors is a "dark art," said Jerrl Evans, the managing director of infrastructure and network services at the IT center of Harris County in Texas – the third largest county in the United States.
Although z/OS lists which mainframe workloads are eligible for System z Integrated Information Processor (zIIP) and System z Application Assist Processor (zAAP), it doesn't necessarily indicate how much of the workload will fit on a particular specialty processor, Evans said.
"If you look at the fundamentals of how zIIPs and zAAPs work, not all traffic goes there," Evans said. "If the OS senses that the zIIP or zAAP will be overloaded, it will funnel the work back to the general-purpose processor. It doesn't queue up."
Why does that matter? Because any work that runs on the zIIP or zAAP processor doesn't carry software licensing costs with it. Offloading work to the zIIP or zAAP also frees up space on the central processors to run other workloads.
"We're interested in how much of our workload is eligible to run on zIIP and zAAP, and of that eligible workload, how much is actually executing there and how much is actually executing on the general-purpose processor."
Two weeks ago, Evans got his hands on the new version of BMC Software Inc.'s Performance Assurance, which is now generally available. One of the new features of the software helps users manage mainframe specialty processor use, though it's early to be definitive here. Evans said the software will help optimize the massive Harris County Justice Information Management System (JIMS) application, which uses a lot of Java (good for zAAP) and a lot of DB2 (good for zIIP).
Complicating matters with zIIP and zAAP
"What BMC has done is be the first to the marketplace with performance management software addressing those processors in particular," said Andi Mann, the research director at Boulder, Colo.-based analyst firm Enterprise Management Associates.
Without an automated tool, Mann said the manual task of figuring out how much work could be offloaded successfully – and how that could affect the overall mainframe – was difficult. Adding a specialty engine introduces another processor that takes resources from a mainframe. That could affect existing processors, which could affect existing workloads.
According to Jay Lipovich, a senior manager at BMC who oversees the Mainview software brand that includes Performance Assurance, zIIPs and zAAPs run at a higher clock speed than a general-purpose processor. "When you add them into the configuration, you can reduce the total capacity of the general-purpose processor, which has a negative impact on all the other work performing," Lipovich said. "It's just the multiprocessor effect that causes that. Our modeling understands those connections."
Harris County runs its JIMS application on a z9 mainframe that has two central processors, one zIIP, one zAAP and an Integrated Facility for Linux (IFL), another specialty engine. Evans said he's spent a lot of time with IBM trying to figure out how much work to offload, but IBM often pushed for the company to just buy another specialty processor. The specialty processors sell for about $100,000 each.
"We can't make investments like that," he said. "We need to determine when to make an investment. You don't want to overbuy, because over time the prices go down and you've wasted the organization's money."
Another new feature of BMC's software helps users correlate business processes with mainframe workloads. An insurance company, for example, can use the software to determine how much mainframe capacity it needs in the event of a 20% increase in claims over two years. Mann said it's a valuable feature, automating a process that is usually "done by experts using spreadsheets and hand calculations."
The cost of BMC Performance Assurance depends on the type of mainframe and license. As an example, pricing for a z10 s401 – the smallest z10 mainframe IBM offers – starts at about $21,000 per year for a three-year term.
Dig Deeper on Data center capacity planning