Digging Into the zIIP: What Does zIIP Eligible Mean?

In the first article in this series on mainframe specialty processors, the zIIP is an “information” processor, where the IIP in its name stands for Integrated Information Processor. When the zIIP was introduced by IBM in 2006, DB2 Version 8 was the first subsystem to take advantage of the zIIP. Over the course of the ensuing years, IBM (and other vendors) have enabled additional workload eligible to be redirected to the zIIP. It stands to reason that the zIIP will be attractive to Db2 users.

That last sentence brings up two terms that need to be defined: eligible and redirect. Workload is zIIP eligible when it runs in an enclave SRB. We will discuss what this means in more detail in the next post in this series. It is important to understand that only certain types of workload are eligible for running on the zIIP. And there is the term “redirect“. Simply because a workload is zIIP eligible does not mean it will run on the zIIP. The workload must be redirected from the general-purpose CPU to the zIIP, meaning that if the system tries to run the workload on the zIIP, which may or may not happen.

Only specific types of workloads are eligible to be redirected to zIIPs. Let’s consider those.

The first set of zIIP eligible workloads to consider is from a Db2 for z/OS perspective. Distributed Db2 for z/OS workload and XML processing can be redirected to zIIP processors. However, to be a bit more precise, these workloads can benefit from zIIPs:

    • Remote SQL requests using DRDA to access Db2, including JDBC and ODBC access to Db2, and native REST calls made over HTTP. This includes native SQL stored procedures that run over a DDF distributed connection. Up to 60% of the workload for these Db2 SQL requests is eligible for redirection to the zIIP.

Even though the zIIP was initially designed for Db2 workload, IBM has made several other types of workloads eligible to be redirected to zIIPs. Perhaps the most significant of these additional workloads is Java application programs. Applications written in Java, using IBM MQ as a Java client, or using IBM WebSphere Application Server and z/OS MF, can redirect workload to zIIPs.

Java is one of the world’s most popular programming languages, especially for developing enterprise applications in large organizations. It consistently ranks near the top of the TIOBE index, ranking programming language popularity. Furthermore, many organizations are modernizing their legacy applications to use Java as a part of digital transformation efforts. The ability to redirect Java workload from general-purpose CPUs to zIIPs can provide significant cost savings to organizations with heavily used Java applications.

Additional types of workloads that are zIIP eligible include:

    • IBM z/OS Container Extensions (zCX), which enable the deployment of Linux applications as Docker containers on z/OS as part of a z/OS workload, are eligible to be redirected to zIIPs. IBM zCX is another key contributor to the legacy modernization efforts of many organizations.

Some third-party independent software vendors (ISVs) have zIIP enabled some of their products, too. Check with your ISV software providers what zIIP capabilities and plans for the products you use.

The Bottom Line

There are multiple types of processing that can run on the zIIP, helping to reduce the cost of your monthly IBM software bill. Remember though, that even with zIIPs installed, all potential workloads will not be redirected to the zIIP – only a percentage of it. Some people refer to the amount of workload that can be redirected as the IBM “generosity factor.”

But understanding zIIPs and prudently using them can save you money.

Craig Mullins, Copyright Craig Mullins Consulting, Inc

30 Jan 2024

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