Mainframe Unix System Services
Today’s mainframe computers - and I’m referring specifically to IBM
zSeries and corresponding z/OS - are an incredibly versatile resource.
Many people already know that mainframes can run Linux in its own VM,
side-by-side with z/OS, and this is a great option for running
Linux-native applications on the mainframe. But most mainframe
shops today have deep roots in batch z/OS and CICS. How do you make use
of new technologies and skill sets (including new hires with little or
no experience with Cobol), without totally rewriting your applications?
Part
of the answer is to make use of z/OS Unix System Services (aka, “USS”).
USS is a complete, Posix-compliant Unix operating environment that is
included with z/OS. It is important to understand that USS is native to
z/OS, not an add-on, and not an emulated virtual machine - so it is
very fast, the same as any native z/OS application. WebSphere, for
example, is a USS application.
Why is USS important? Because it
provides a bridge from old to new: You can hire from the plentiful
Unix-experienced talent pool to work on your mainframe applications!
From
within USS, you can compile applications in any language supported by
the mainframe, run them in batch or as started tasks, and can even
compile CICS applications using the CICS translator. USS includes its
own Hierarchical File System (HFS), but since USS also fully supports
JCL, it can equally access traditional resources just as well,
including VSAM files. Note that the JCL support is fully
bi-directional: Traditional Cobol applications can use JCL to access
HFS files, and USS applications can use JCL to access traditional
mainframe resources.
Since USS supports a full Unix environment
and HFS, this also means that USS developers can use traditional Unix
tools - including Java, C, C++, Make, CVS & Subversion (version
control systems), and so on - to develop or enhance mainframe applications running under batch, CICS, etc.
I’ll demonstrate some examples in a future post.
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