Don Appleby's Blog

Continuing with our thread on mainframes for project managers:

In addition to the general purpose (GP) engines on the mainframe, you can also add specialty engines.  Specialty engines, as the name implies, are intended to provide very specific processing capabilities in contrast to the generalized processing capabilities of the general purpose engines.

There are four main types of specialty engines: IFLs, zIIPs, zAAPs, and ICFs.

IFL stands for Integrated Facility for Linux. With an IFL, you can run either native zLinux or zLinux under zVM.  You could also run them in a GP engine, but adding a GP tends to raise your overall software costs on a mainframe, whereas running them in an IFL does not.  For that reason, adding IFLs is an effective strategy for reducing the total cost of ownership (TCO) on a mainframe.

zIIP engines support certain DB2 functions.  A zIIP then becomes a way of offloading some workload from the GP engines – another effective strategy for TCO.

zAAP engines support Java.  Like the zIIP, the zAAP allows certain workloads to be offloaded from the GP engines.  (Note: Some zAAP functionality is now available in the zIIP, so you may hear the phrase “zAAP on zIIP.”   It’s possible that a zIIP may handle both your zIIP and zAAP eligible workloads.

ICF stands for Integrated Coupling Facility.  ICFs run something called CFCC (Coupling Facility Control Code) and are used in what is known as a parallel sysplex environment.  Think of the ICF as a key element in a design that requires data sharing.

There are two noteworthy things at work here:

1. As you increase the number and speed of GP engines, the “rated capacity” on your mainframe increases, resulting in higher software costs.  For that reason, using specialty engines (which don’t count toward “rated capacity” ) to offload the GP engines may help you reduce your GP capacity requirements.   For example, suppose my aggregate workload would require four GP engines – but, if I offload some of that workload to specialty engines, then perhaps I only need three GP engines.  That ultimately translates into software savings.

2. Note also that the specialty engines are (to a great extent) intended for DB2, Java, and Linux workloads.  You cannot run zOS or zVSE in a specialty engine.  You can run zVM in an IFL, but it’s there to provide virtualization capability for zLinux (RedHat or SUSE).  The strengths of the mainframe (resiliency, reliability, I/O bandwidth, to name a few) can be matched to new workloads – not just to the traditional mainframe operating systems.