What is CICS Application Multi-versioning?
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In CICS TS V5.1 we introduced the application resource with a nice long 64-character name and a proper version. So rather than just borrowing characters from an 8 character CICS resource definition name, it was now possible to track application changes through development, deployment, runtime, and even measurement using CICS Monitoring data. One restriction remained: you could only install one version of an application at a time. This is because if version 1.0.0 of your home loan application contains a program called ADDCSTMR, then version 1.1.0 is likely to have one too, and you can’t install both into CICS at the same time. Well, at least until now. But why would you want to?
In this first of a series of articles on the technology I will start with a simple example of how the multi-versioning capability as part of our cloud enablement strategy can help with another of our big items: operational efficiency. You have two independently developed applications that use the same program names so they must be deployed onto different CICS regions. But you want to consolidate your infrastructure to save cost, taking advantage of the continued improvement in scalability in CICS TS V5.2. How can CICS application multi-versioning help?
Each application contains a program called ADDCSTMR so must be installed into separate CICS regions
By packaging each as a CICS application you can hide these clashing program names from each other. How does this work? Each application requires a unique dynamic program LIBRARY resource with its own dataset from where the different implementations of the ADDCSTMR (add customer) program are loaded. The difference in CICS TS V5.2 is that a program LIBRARY defined by a CICS application resource is not added to the global search path along with DFHRPL. Instead, it is searched first for any PROGRAM resources unique to the application. The two applications can now be installed into the same CICS region.
Each implementation of program ADDCSTMR is loaded from a separate dataset defined in an application-unique program LIBRARY so the applications can be installed into the same CICS region
In this article we have shown how CICS application multi-versioning can help with server consolidation. But this new technology is about more than dealing with PROGRAM resource name clashes. In the next post I will describe how you can quickly and reliably apply or back-out an application update.
For more information please the Cloud enablement section of the CICS Transaction Server 5.2.0 open beta Knowledge Center.