Anyone who uses an IBM z Series mainframe has probably heard about zIIPs and zAAPs and other specialty processors. But maybe you haven't yet done any real investigation into what they are, what they do, and why they exist. So, with that in mind, let's take a brief journey into the world of specialty processors in today's blog entry!
Over the course of the past decade or so,IBM has introduced several different types of specialty processors. The basic idea of a specialty processor, is that it sits alongside the main CPUs and specific types of "special" workload is shuttled to the specialty processor to be run there, instead of on the primary CPU complex. Why is this useful or interesting to mainframe customers? Well, the specialty processor workload is not subject to IBM or ISV licensing charges... and, as any mainframer knows, the cost of software rises as capacity on the mainframe rises. But if capacity can be redirected to a specialty processor, then software license charges do not accrue -- at least for that workload.
Another benefit of the specialty processors is that they are significantly cheaper to acquire than standard CPUs. A standard mainframe CP costs around $250K, whereas a specialty processor costs less than $50K -- less than one fifth the price of the standard processor.
But there is a catch! The specialty processors can only run certain types of workloads -- at least that is so as configured by IBM "out of the box."
There are four types of specialty processors:
- ICF: Internal Coupling Facility - used for redirecting coupling facility cycles in a data sharing environment.
- IFL: Integrated Facility for Linux - used for processing zLinux workload on an IBM mainframe.
- zAAP: Application Assist Processor - used for the Java virtual machine
- zIIP: Integrated Information Processor - used for processing certain, distributed database workloads.
When you activate any of these processors, some percentage of that type of workload can be redirected off of the main CP onto the specialty processor... but not 100% of the workload. Indeed, one of the frustrating issues, particularly with the zIIP, is that it is difficult to understand exactly what is redirected exactly when and exactly how much of it. In general, distributed DB2 for z/OS workload and XML processing can be redirected to zIIP processors.
Additionally, to run on a zIIP, the workload must run under an enclave SRB.So, code written to execute under a TCB will usually be unable to execute under an SRB without major changes. If you didn't understand that sentence, don't worry about it too much. If you are interested, more details about zIIPs can be found at this link.
The bottom line though is that specialty processors can help to reduce the cost of mainframe computing... and there will be software innovations coming to help organization more effectivly utilize specialty processors for more and varied types of workloads...